Episode 8 — Aptitude and Reasoning / 8.3 — Simple Interest
8.3 Practice MCQs -- Simple Interest
Instructions: Each question has four options. Choose the correct one. Solutions are provided in the Answer Key at the end.
Time Target: 1-1.5 minutes per question.
SECTION A: BASIC (Questions 1-15)
Q1. Find the Simple Interest on Rs. 5000 at 6% per annum for 4 years.
(a) Rs. 1000 (b) Rs. 1200 (c) Rs. 1400 (d) Rs. 1100
Q2. What is the amount when Rs. 8000 is invested at 9% per annum simple interest for 3 years?
(a) Rs. 10,160 (b) Rs. 10,240 (c) Rs. 9920 (d) Rs. 10,080
Q3. A sum of money earns Rs. 630 as SI in 3 years at 7% per annum. Find the principal.
(a) Rs. 2500 (b) Rs. 3000 (c) Rs. 3500 (d) Rs. 4000
Q4. At what rate percent per annum will Rs. 4000 earn Rs. 1200 as simple interest in 5 years?
(a) 5% (b) 6% (c) 8% (d) 4%
Q5. In what time will Rs. 1500 amount to Rs. 1800 at 8% per annum simple interest?
(a) 2 years (b) 3 years (c) 2.5 years (d) 4 years
Q6. Find the SI on Rs. 7200 at 5% per annum for 9 months.
(a) Rs. 270 (b) Rs. 360 (c) Rs. 540 (d) Rs. 180
Q7. At what rate of simple interest will a sum double itself in 10 years?
(a) 8% (b) 10% (c) 12% (d) 15%
Q8. The SI on Rs. 10,000 at a certain rate for 2 years is Rs. 1600. Find the rate.
(a) 6% (b) 7% (c) 8% (d) 9%
Q9. What principal will amount to Rs. 13,200 in 4 years at 8% per annum SI?
(a) Rs. 10,000 (b) Rs. 10,200 (c) Rs. 10,500 (d) Rs. 10,800
Q10. If Rs. 600 amounts to Rs. 744 in 4 years, find the rate of simple interest.
(a) 5% (b) 6% (c) 7% (d) 8%
Q11. The SI on a certain sum is 1/4 of the principal. If the rate is 5% per annum, find the time.
(a) 4 years (b) 5 years (c) 6 years (d) 8 years
Q12. Find the SI on Rs. 2400 at 12.5% per annum for 2 years.
(a) Rs. 500 (b) Rs. 600 (c) Rs. 700 (d) Rs. 480
Q13. Rs. 1000 is invested at 10% SI. After how many years will the amount become Rs. 1500?
(a) 4 years (b) 5 years (c) 6 years (d) 3 years
Q14. The SI on a sum for 5 years is 2/5 of the sum. Find the rate per annum.
(a) 6% (b) 8% (c) 10% (d) 12%
Q15. A man deposits Rs. 3000 in a bank at 8% SI. How much will he get after 2 years 6 months?
(a) Rs. 3600 (b) Rs. 3500 (c) Rs. 3480 (d) Rs. 3750
SECTION B: MEDIUM (Questions 16-30)
Q16. A sum becomes Rs. 6200 in 3 years and Rs. 7400 in 5 years at SI. Find the principal.
(a) Rs. 4000 (b) Rs. 4200 (c) Rs. 4400 (d) Rs. 4800
Q17. Rahul borrows Rs. 12,000 at 9% SI and lends it at 13% SI for 3 years. His gain is:
(a) Rs. 1200 (b) Rs. 1440 (c) Rs. 1560 (d) Rs. 1680
Q18. Rs. 5600 is divided into two parts. SI on the first part at 6% for 3 years equals SI on the second part at 8% for 3 years. Find the first part.
(a) Rs. 2800 (b) Rs. 3000 (c) Rs. 3200 (d) Rs. 3400
Q19. In how many years will a sum of money triple at 12.5% per annum SI?
(a) 14 years (b) 16 years (c) 18 years (d) 20 years
Q20. A sum doubles in 8 years at SI. In how many years will it become 5 times?
(a) 28 years (b) 30 years (c) 32 years (d) 40 years
Q21. The SI on Rs. 5000 for 2 years at R% is equal to the SI on Rs. 4000 for 3 years at 5%. Find R.
(a) 5% (b) 6% (c) 7% (d) 8%
Q22. Rs. 25,000 is invested in two parts at 10% and 12% per annum SI. If the total annual interest is Rs. 2700, find the amount invested at 10%.
(a) Rs. 15,000 (b) Rs. 12,000 (c) Rs. 18,000 (d) Rs. 10,000
Q23. Find the SI on Rs. 8000 at 5% for the first 3 years and 8% for the next 2 years.
(a) Rs. 2280 (b) Rs. 2480 (c) Rs. 2400 (d) Rs. 2560
Q24. A certain sum amounts to Rs. 14,800 in 4 years at 12% SI. What will it amount to in 6 years at the same rate?
(a) Rs. 16,800 (b) Rs. 17,200 (c) Rs. 17,600 (d) Rs. 18,000
Q25. The difference between the SI on a certain sum at 10% for 6 years and at 8% for 8 years is Rs. 80. Find the sum.
(a) Rs. 1500 (b) Rs. 2000 (c) Rs. 4000 (d) Rs. 8000
Q26. A sum of Rs. 9000 is lent in two parts, one at 7% and the other at 9% per annum SI. If the total annual interest is Rs. 710, find the sum lent at 9%.
(a) Rs. 3500 (b) Rs. 4000 (c) Rs. 4500 (d) Rs. 5500
Q27. A sum of money becomes 8/5 of itself in 4 years at SI. Find the rate of interest.
(a) 12% (b) 12.5% (c) 15% (d) 16%
Q28. Priya borrows Rs. 20,000 at 10% SI. She returns Rs. 10,000 at the end of year 1. What amount does she need to pay at the end of year 2 to clear the debt?
(a) Rs. 12,800 (b) Rs. 13,000 (c) Rs. 13,200 (d) Rs. 12,000
Q29. The SI on a sum at 4% per annum for 3 years and 6 months is Rs. 2100. Find the sum.
(a) Rs. 12,000 (b) Rs. 14,000 (c) Rs. 15,000 (d) Rs. 16,000
Q30. A man deposits Rs. 5000 at the beginning of each year for 3 years at 8% SI. Find the total interest at the end of 3 years.
(a) Rs. 2000 (b) Rs. 2400 (c) Rs. 1200 (d) Rs. 3600
SECTION C: ADVANCED (Questions 31-42)
Q31. A sum of money at SI amounts to Rs. 5600 in 4 years and Rs. 6800 in 7 years. The rate of interest per annum is:
(a) 8% (b) 10% (c) 12% (d) 9%
Q32. Rs. 6000 becomes Rs. 7200 in 4 years at a certain rate of SI. If the rate were increased by 2%, what would be the new amount?
(a) Rs. 7500 (b) Rs. 7680 (c) Rs. 7800 (d) Rs. 8000
Q33. A man borrows Rs. 10,000 at 8% SI and Rs. 15,000 at 6% SI, both for the same period. If he pays a total of Rs. 5100 as interest, find the period.
(a) 2 years (b) 2.5 years (c) 3 years (d) 3.5 years
Q34. Two equal sums were invested at 8% and 12% SI respectively. The difference in interest after 4 years was Rs. 640. Each sum is:
(a) Rs. 2000 (b) Rs. 3000 (c) Rs. 4000 (d) Rs. 5000
Q35. A sum was invested at SI at a certain rate for 3 years. Had it been invested at 4% higher rate, it would have earned Rs. 720 more. Find the sum.
(a) Rs. 4000 (b) Rs. 5000 (c) Rs. 6000 (d) Rs. 7000
Q36. A person invests Rs. 10,000 for 2 years at 10% SI. At the end of 2 years, he reinvests the entire amount (principal + interest) for another 3 years at 8% SI. What is the total amount at the end of 5 years?
(a) Rs. 14,680 (b) Rs. 14,880 (c) Rs. 15,080 (d) Rs. 14,280
Q37. The SI on a sum for 2 years at 10% per annum is Rs. 1000. The compound interest on the same sum for 2 years at the same rate is:
(a) Rs. 1000 (b) Rs. 1050 (c) Rs. 1100 (d) Rs. 1025
Q38. A lends Rs. 2500 to B at 10% SI and B lends the same to C at 12% SI. After 3 years, B's gain in the transaction is:
(a) Rs. 100 (b) Rs. 150 (c) Rs. 200 (d) Rs. 250
Q39. The annual interest earned on an investment decreases by Rs. 450 when the rate decreases from 12% to 9%. The investment amount is:
(a) Rs. 10,000 (b) Rs. 12,000 (c) Rs. 15,000 (d) Rs. 18,000
Q40. A man invested 1/3 of his capital at 7%, 1/4 at 8%, and the remaining at 10% per annum SI. If his annual income is Rs. 510, find his capital.
(a) Rs. 5000 (b) Rs. 6000 (c) Rs. 5400 (d) Rs. 6600
Q41. A sum of money at 8% SI per annum becomes 7/4 of itself. In how many years does this happen?
(a) 8 years (b) 9 years (c) 9.375 years (d) 10 years
Q42. Rs. 2000 is invested at 10% SI for 2 years. The interest earned is then invested at 8% SI for 3 years. What is the total interest earned from both investments?
(a) Rs. 400 (b) Rs. 496 (c) Rs. 520 (d) Rs. 480
ANSWER KEY WITH DETAILED EXPLANATIONS
Q1. Answer: (b) Rs. 1200
SI = (P x R x T) / 100
SI = (5000 x 6 x 4) / 100
SI = 120000 / 100
SI = Rs. 1200
Q2. Answer: (a) Rs. 10,160
SI = (8000 x 9 x 3) / 100 = 216000 / 100 = Rs. 2160
Amount = P + SI = 8000 + 2160 = Rs. 10,160
Q3. Answer: (b) Rs. 3000
P = (SI x 100) / (R x T)
P = (630 x 100) / (7 x 3)
P = 63000 / 21
P = Rs. 3000
Q4. Answer: (b) 6%
R = (SI x 100) / (P x T)
R = (1200 x 100) / (4000 x 5)
R = 120000 / 20000
R = 6%
Q5. Answer: (c) 2.5 years
SI = A - P = 1800 - 1500 = Rs. 300
T = (SI x 100) / (P x R)
T = (300 x 100) / (1500 x 8)
T = 30000 / 12000
T = 2.5 years
Q6. Answer: (a) Rs. 270
T = 9 months = 9/12 = 3/4 years
SI = (7200 x 5 x 3/4) / 100
SI = (7200 x 3.75) / 100
SI = 27000 / 100
SI = Rs. 270
Q7. Answer: (b) 10%
When amount doubles: A = 2P, so SI = P.
R x T = 100
R x 10 = 100
R = 10%
Q8. Answer: (c) 8%
R = (SI x 100) / (P x T)
R = (1600 x 100) / (10000 x 2)
R = 160000 / 20000
R = 8%
Q9. Answer: (a) Rs. 10,000
A = P(100 + RT) / 100
13200 = P(100 + 8 x 4) / 100
13200 = P x 132 / 100
P = (13200 x 100) / 132
P = Rs. 10,000
Verification: SI = (10000 x 8 x 4)/100 = 3200
A = 10000 + 3200 = 13200 [Correct]
Q10. Answer: (b) 6%
SI = 744 - 600 = Rs. 144
R = (144 x 100) / (600 x 4)
R = 14400 / 2400
R = 6%
Q11. Answer: (b) 5 years
SI = P/4
(P x 5 x T) / 100 = P/4
5T/100 = 1/4
T = 100/20 = 5 years
Q12. Answer: (b) Rs. 600
12.5% = 1/8
SI per year = 2400 / 8 = Rs. 300
SI for 2 years = 300 x 2 = Rs. 600
Q13. Answer: (b) 5 years
SI = 1500 - 1000 = Rs. 500
T = (500 x 100) / (1000 x 10)
T = 50000 / 10000
T = 5 years
Q14. Answer: (b) 8%
SI = (2/5)P
(P x R x 5) / 100 = 2P/5
5R/100 = 2/5
R = (2 x 100) / (5 x 5) = 200/25 = 8%
Q15. Answer: (a) Rs. 3600
T = 2 years 6 months = 2.5 years
SI = (3000 x 8 x 2.5) / 100 = 60000/100 = Rs. 600
Amount = 3000 + 600 = Rs. 3600
Q16. Answer: (c) Rs. 4400
SI per year = (7400 - 6200) / (5 - 3) = 1200/2 = Rs. 600
SI for 3 years = 600 x 3 = Rs. 1800
P = 6200 - 1800 = Rs. 4400
Verification:
R = (600 x 100) / 4400 = 60000/4400 = 150/11 ≈ 13.64%
A at T=5: 4400 + 600x5 = 4400 + 3000 = 7400 [Correct]
Q17. Answer: (b) Rs. 1440
Gain = P x (R_lend - R_borrow) x T / 100
Gain = 12000 x (13 - 9) x 3 / 100
Gain = 12000 x 4 x 3 / 100
Gain = 144000 / 100
Gain = Rs. 1440
Q18. Answer: (c) Rs. 3200
Let first part = x, second part = 5600 - x.
SI on first = SI on second (same time period):
(x x 6 x 3) / 100 = ((5600 - x) x 8 x 3) / 100
Cancel /100 and x3 from both sides:
6x = (5600 - x) x 8
6x = 44800 - 8x
14x = 44800
x = 3200
First part = Rs. 3200
Verification:
SI1 = (3200 x 6 x 3)/100 = 576
SI2 = (2400 x 8 x 3)/100 = 576 [Equal. Correct]
Q19. Answer: (b) 16 years
Amount triples: A = 3P, so SI = 2P.
R x T = 200
12.5 x T = 200
T = 200 / 12.5 = 16 years
Q20. Answer: (c) 32 years
Doubles in 8 years means R x 8 = 100, so R = 12.5%.
For 5 times: R x T = (5-1) x 100 = 400
12.5 x T = 400
T = 32 years
Shortcut: Time to become n times = (n-1) x (time to double)
= (5-1) x 8 = 32 years
Q21. Answer: (b) 6%
(5000 x R x 2) / 100 = (4000 x 5 x 3) / 100
10000R = 60000
R = 6%
Q22. Answer: (a) Rs. 15,000
Let amount at 10% = x, then at 12% = (25000 - x).
10x/100 + 12(25000-x)/100 = 2700
10x + 300000 - 12x = 270000
-2x = -30000
x = 15000
Verification: (15000x10)/100 + (10000x12)/100 = 1500+1200 = 2700 [Correct]
Q23. Answer: (b) Rs. 2480
SI = P x (R1.T1 + R2.T2) / 100
SI = 8000 x (5x3 + 8x2) / 100
SI = 8000 x (15 + 16) / 100
SI = 8000 x 31 / 100
SI = Rs. 2480
Q24. Answer: (b) Rs. 17,200
A in 4 years = 14800, R = 12%
P = (A x 100) / (100 + RT)
P = (14800 x 100) / (100 + 48)
P = 1480000 / 148
P = Rs. 10,000
A in 6 years:
SI = (10000 x 12 x 6) / 100 = Rs. 7200
A = 10000 + 7200 = Rs. 17,200
Verification: SI for 4 years = (10000x12x4)/100 = 4800
A at 4 years = 10000+4800 = 14800 [Correct]
Q25. Answer: (b) Rs. 2000
SI at 10% for 6 years = P x 60/100 = 0.60P
SI at 8% for 8 years = P x 64/100 = 0.64P
The 8%-for-8-years investment gives MORE interest.
Difference = 0.64P - 0.60P = 0.04P = 80
P = 80 / 0.04 = Rs. 2000
Q26. Answer: (b) Rs. 4000
Let sum at 7% = x, then sum at 9% = (9000 - x).
7x/100 + 9(9000-x)/100 = 710
7x + 81000 - 9x = 71000
-2x = -10000
x = 5000
Sum at 7% = Rs. 5000
Sum at 9% = 9000 - 5000 = Rs. 4000
Verification: (5000x7)/100 + (4000x9)/100 = 350 + 360 = 710 [Correct]
Q27. Answer: (c) 15%
A = (8/5)P
SI = A - P = (8/5)P - P = (3/5)P
(P x R x 4) / 100 = (3/5)P
4R/100 = 3/5
R = (3 x 100) / (5 x 4) = 300/20 = 15%
Q28. Answer: (c) Rs. 13,200
Year 1:
Interest = (20000 x 10 x 1)/100 = Rs. 2000
Amount due at end of year 1 = 20000 + 2000 = Rs. 22,000
Payment = Rs. 10,000
Remaining = 22000 - 10000 = Rs. 12,000
Year 2:
Interest on remaining = (12000 x 10 x 1)/100 = Rs. 1200
Amount due at end of year 2 = 12000 + 1200 = Rs. 13,200
Q29. Answer: (c) Rs. 15,000
T = 3 years 6 months = 7/2 years
P = (SI x 100) / (R x T)
P = (2100 x 100) / (4 x 7/2)
P = 210000 / 14
P = Rs. 15,000
Q30. Answer: (b) Rs. 2400
Deposit 1: Rs. 5000 for 3 years -> SI = (5000x8x3)/100 = Rs. 1200
Deposit 2: Rs. 5000 for 2 years -> SI = (5000x8x2)/100 = Rs. 800
Deposit 3: Rs. 5000 for 1 year -> SI = (5000x8x1)/100 = Rs. 400
Total SI = 1200 + 800 + 400 = Rs. 2400
Q31. Answer: (b) 10%
SI per year = (6800 - 5600) / (7 - 4) = 1200/3 = Rs. 400
SI for 4 years = 400 x 4 = Rs. 1600
P = 5600 - 1600 = Rs. 4000
R = (SI per year x 100) / P
R = (400 x 100) / 4000
R = 40000 / 4000
R = 10%
Verification:
A at 4 years = 4000 + (4000x10x4)/100 = 4000+1600 = 5600 [Correct]
A at 7 years = 4000 + (4000x10x7)/100 = 4000+2800 = 6800 [Correct]
Q32. Answer: (b) Rs. 7680
Original: SI = 7200 - 6000 = Rs. 1200 in 4 years
R = (1200 x 100) / (6000 x 4) = 120000/24000 = 5%
New rate = 5 + 2 = 7%
New SI = (6000 x 7 x 4) / 100 = 168000/100 = Rs. 1680
New amount = 6000 + 1680 = Rs. 7680
Q33. Answer: (c) 3 years
Total interest = (10000 x 8 x T)/100 + (15000 x 6 x T)/100
= 800T + 900T
= 1700T
1700T = 5100
T = 5100 / 1700 = 3 years
Verification:
SI1 = (10000 x 8 x 3)/100 = 2400
SI2 = (15000 x 6 x 3)/100 = 2700
Total = 2400 + 2700 = 5100 [Correct]
Q34. Answer: (c) Rs. 4000
Let each sum = P.
SI at 12% for 4 years - SI at 8% for 4 years = 640
P x (12 - 8) x 4 / 100 = 640
P x 16 / 100 = 640
P = (640 x 100) / 16
P = Rs. 4000
Q35. Answer: (c) Rs. 6000
Extra SI from 4% higher rate for 3 years:
P x 4 x 3 / 100 = 720
12P / 100 = 720
P = (720 x 100) / 12
P = Rs. 6000
Q36. Answer: (b) Rs. 14,880
Phase 1: P = 10000, R = 10%, T = 2 years
SI = (10000 x 10 x 2)/100 = Rs. 2000
Amount after 2 years = 10000 + 2000 = Rs. 12,000
Phase 2: P = 12000, R = 8%, T = 3 years
SI = (12000 x 8 x 3)/100 = Rs. 2880
Amount after 5 years = 12000 + 2880 = Rs. 14,880
Q37. Answer: (b) Rs. 1050
SI for 2 years at 10% = Rs. 1000
P = (1000 x 100) / (10 x 2) = Rs. 5000
CI for 2 years at 10%:
CI = P[(1 + R/100)^2 - 1]
CI = 5000[(1.1)^2 - 1]
CI = 5000[1.21 - 1]
CI = 5000 x 0.21
CI = Rs. 1050
Alternative: CI - SI for 2 years = P(R/100)^2 = 5000 x 0.01 = 50
So CI = 1000 + 50 = Rs. 1050
Q38. Answer: (b) Rs. 150
B pays A interest at 10%: (2500 x 10 x 3)/100 = Rs. 750
B receives from C at 12%: (2500 x 12 x 3)/100 = Rs. 900
B's gain = 900 - 750 = Rs. 150
Q39. Answer: (c) Rs. 15,000
Decrease in annual interest = P x (12 - 9)/100 = 3P/100
3P/100 = 450
P = (450 x 100) / 3
P = Rs. 15,000
Q40. Answer: (b) Rs. 6000
Let capital = C.
Remaining fraction = 1 - 1/3 - 1/4 = (12-4-3)/12 = 5/12
Annual income:
= (C/3 x 7)/100 + (C/4 x 8)/100 + (5C/12 x 10)/100
= 7C/300 + 8C/400 + 50C/1200
= 7C/300 + C/50 + 5C/120
LCM of 300, 50, 120 = 600:
= 14C/600 + 12C/600 + 25C/600
= 51C/600
= 17C/200
17C/200 = 510
C = (510 x 200) / 17
C = 102000 / 17
C = Rs. 6000
Verification:
1/3 of 6000 = 2000 at 7% -> 140
1/4 of 6000 = 1500 at 8% -> 120
5/12 of 6000 = 2500 at 10% -> 250
Total = 140 + 120 + 250 = 510 [Correct]
Q41. Answer: (c) 9.375 years
A = (7/4)P
SI = A - P = (7/4)P - P = (3/4)P
(P x 8 x T) / 100 = (3/4)P
8T/100 = 3/4
T = (3 x 100) / (4 x 8)
T = 300/32
T = 9.375 years (or 9 years 4.5 months)
Q42. Answer: (b) Rs. 496
Step 1: Interest from first investment
SI1 = (2000 x 10 x 2) / 100 = Rs. 400
Step 2: This Rs. 400 is invested at 8% for 3 years
SI2 = (400 x 8 x 3) / 100 = Rs. 96
Total interest earned = SI1 + SI2 = 400 + 96 = Rs. 496
Quick Answer Reference
BASIC: 1(b) 2(a) 3(b) 4(b) 5(c) 6(a) 7(b) 8(c)
9(a) 10(b) 11(b) 12(b) 13(b) 14(b) 15(a)
MEDIUM: 16(c) 17(b) 18(c) 19(b) 20(c) 21(b) 22(a) 23(b)
24(b) 25(b) 26(b) 27(c) 28(c) 29(c) 30(b)
ADVANCED: 31(b) 32(b) 33(c) 34(c) 35(c) 36(b) 37(b) 38(b)
39(c) 40(b) 41(c) 42(b)
Score Interpretation
35-42 correct: Excellent! You have mastered Simple Interest.
28-34 correct: Good. Review the problems you missed.
20-27 correct: Fair. Revisit the Concepts and Tips sections.
Below 20: Needs significant practice. Start from basics again.
Next: 8.3 Quick Revision