Practice Questions
Concept Explanation
Simple Interest (SI) is calculated only on the original principal for the entire period. Interest does not earn further interest.
Key Formula
SI = (P × R × T) / 100
- P = Principal (initial sum)
- R = Rate of interest per annum (%)
- T = Time in years
Amount
Amount (A) = P + SI
Example
Find SI on Rs. 5,000 at 10% per annum for 2 years.
SI = (5000 × 10 × 2) / 100 = Rs. 1,000. Amount = Rs. 6,000.
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Q1 EasyFind SI on Rs. 3000 at 8% for 3 years.ExplanationFormula: SI = (P × R × T) / 100. Here P = 3000, R = 8 and T = 3. SI = (3000 × 8 × 3) / 100 = 72000 / 100 = Rs. 720. Hence the answer is Rs. 720.
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Q2 EasyPrincipal Rs. 8000, rate 5%, time 4 years — SI and amount.ExplanationFormula: SI = (P × R × T) / 100 and Amount = P + SI. SI = (8000 × 5 × 4) / 100 = 160000 / 100 = Rs. 1,600. Amount = 8000 + 1600 = Rs. 9,600. Hence SI = Rs. 1,600 and Amount = Rs. 9,600.
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Q3 EasyWhat will be the ratio of simple interest earned by certain amount at the same rate of interest for 6 years and that for 9 years?ExplanationFormula: SI = (P × R × T) / 100. At the same P and R, SI is proportional to T. Required ratio = SI for 6 years : SI for 9 years = 6 : 9 = 2 : 3. Hence the answer is 2 : 3.
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Q4 EasyFind the simple interest on Rs. 7,500 at 8% per annum for 2 years.ExplanationFormula: SI = (P × R × T) / 100. SI = (7500 × 8 × 2) / 100 = 120000 / 100 = Rs. 1,200. Hence the answer is Rs. 1,200.
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Q5 EasyA sum of Rs. 10,000 is lent at 12% simple interest per annum for 3 years. What is the amount payable at the end of 3 years?ExplanationFormula: SI = (P × R × T) / 100 and Amount = P + SI. SI = (10000 × 12 × 3) / 100 = Rs. 3,600. Amount = 10000 + 3600 = Rs. 13,600. Hence the answer is Rs. 13,600.
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Q6 EasyA campus placement aptitude question asks: SI on Rs. 2,500 at 10% for 1.5 years equals:ExplanationFormula: SI = (P × R × T) / 100. SI = (2500 × 10 × 1.5) / 100 = 37500 / 100 = Rs. 375. Hence the answer is Rs. 375.
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Q7 EasyThe amount on Rs. 6,000 at 8% simple interest for 5 years is:ExplanationFormula: SI = (P × R × T) / 100 and Amount = P + SI. SI = (6000 × 8 × 5) / 100 = Rs. 2,400. Amount = 6000 + 2400 = Rs. 8,400. Hence the answer is Rs. 8,400.
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Q8 MediumA person borrows Rs. 5000 for 2 years at 4% p.a. simple interest. He immediately lends it to another person at 6¼% p.a. for 2 years. Find his gain in the transaction per year.ExplanationFormula: SI = (P × R × T) / 100. Interest paid in 2 years = (5000 × 4 × 2) / 100 = Rs. 400. Interest received in 2 years = (5000 × 25/4 × 2) / 100 = (5000 × 6.25 × 2) / 100 = Rs. 625. Gain in 2 years = 625 − 400 = Rs. 225. Gain per year = 225 / 2 = Rs. 112.50. Hence the answer is Rs. 112.50.
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Q9 MediumWhat will be the simple interest earned on an amount of Rs. 16,800 in 9 months at the rate of 6¼% p.a.?ExplanationFormula: SI = (P × R × T) / 100. Here T = 9/12 = 3/4 year and R = 25/4%. SI = (16800 × 25/4 × 3/4) / 100 = (16800 × 25 × 3) / (16 × 100) = 1260000 / 1600 = Rs. 787.50. Hence the answer is Rs. 787.50.
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Q10 MediumThe simple interest on Rs. 5,000 at 6% per annum for 4 years is equal to the simple interest on Rs. X at 5% per annum for 6 years. Find X.ExplanationFormula: SI = (P × R × T) / 100. Given (5000 × 6 × 4)/100 = (X × 5 × 6)/100. So 120000 = 30X, hence X = 120000 / 30 = Rs. 4,000. Hence the answer is Rs. 4,000.
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Q11 MediumIf the simple interest on a sum for 3 years at 7% per annum is Rs. 1,260, what is the amount after 3 years?ExplanationFormula: P = (100 × SI) / (R × T) and Amount = P + SI. P = (100 × 1260) / (7 × 3) = 126000 / 21 = Rs. 6,000. Amount = 6000 + 1260 = Rs. 7,260. Hence the answer is Rs. 7,260.
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Q12 MediumFind SI on Rs. 9,600 at 7.5% per annum for 2 years.ExplanationFormula: SI = (P × R × T) / 100. SI = (9600 × 7.5 × 2) / 100 = (9600 × 15) / 100 = 144000 / 100 = Rs. 1,440. Hence the answer is Rs. 1,440.
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Q13 HardMr. Thomas invested an amount of Rs. 13,900 divided in two different schemes A and B at the simple interest rate of 14% p.a. and 11% p.a. respectively. If the total amount of simple interest earned in 2 years be Rs. 3508, what was the amount invested in Scheme B?ExplanationFormula: SI = (P × R × T) / 100. Let sum in A be x and sum in B be (13900 − x). Then (x × 14 × 2)/100 + ((13900 − x) × 11 × 2)/100 = 3508. So 28x/100 + 22(13900 − x)/100 = 3508. Multiply by 100: 28x + 305800 − 22x = 350800. Then 6x = 45000, so x = 7500. Amount in Scheme B = 13900 − 7500 = Rs. 6,400. Hence the answer is Rs. 6,400.
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Q14 HardIn a screening test, simple interest on Rs. 4,800 at 9% for 2 years 6 months is asked. The interest is:ExplanationFormula: SI = (P × R × T) / 100. Time = 2.5 years. SI = (4800 × 9 × 2.5) / 100 = (4800 × 22.5) / 100 = 108000 / 100 = Rs. 1,080. Hence the answer is Rs. 1,080.
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DS1 Easy
Trainees must compute the interest earned. What is the simple interest?
Statement IThe principal is Rs. 5,000 and the rate is 10% per annum.
Statement IIThe time period is 2 years.
ExplanationFormula: SI = (P × R × T) / 100. Statement I gives P and R but not T. Statement II gives T but not P and R. Together: SI = (5000 × 10 × 2) / 100 = Rs. 1,000. Both are needed. Answer: C. -
DS2 Easy
Candidates must find the simple interest on a loan. What is the simple interest?
Statement IPrincipal is Rs. 8,000, rate is 5% per annum and time is 4 years.
Statement IIOnly the amount after 4 years is Rs. 9,600 (principal is not stated).
ExplanationFormula: SI = (P × R × T) / 100. Statement I: SI = (8000 × 5 × 4) / 100 = Rs. 1,600, so I alone is sufficient. Statement II gives only the amount, not the principal, so SI cannot be found from II alone. Answer: A.
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DS3 Easy
For the maturity amount of a deposit. What is the amount?
Statement IPrincipal is Rs. 10,000 and rate is 12% per annum.
Statement IITime is 2 years.
ExplanationFormula: Amount = P + (P × R × T) / 100. Statement I lacks T; Statement II lacks P and R. Together: SI = (10000 × 12 × 2) / 100 = Rs. 2,400 and Amount = 10000 + 2400 = Rs. 12,400. Both are needed. Answer: C. -
DS4 Medium
An HR analytics quiz asks whether interest crosses a threshold. Is the simple interest greater than Rs. 1,000?
Statement IPrincipal is Rs. 6,000 at 8% per annum for 2 years.
Statement IIThe time of investment is less than 3 years, but principal and rate are unknown.
ExplanationFormula: SI = (P × R × T) / 100. Statement I: SI = (6000 × 8 × 2) / 100 = Rs. 960, which is not greater than Rs. 1,000, so the answer is No. Statement II alone cannot decide. Statement I alone is sufficient. Answer: A.