Practice Questions
Concept Explanation
When simple interest, rate, and time are known, rearrange the SI formula to find the principal.
Key Formula
P = (100 × SI) / (R × T)
Alternatively, if amount (A) is known: P = A − SI or P = 100A / (100 + RT)
Example
SI = Rs. 900 at 6% for 5 years. P = (100 × 900)/(6 × 5) = Rs. 3,000.
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Q1 Easy
SI is Rs. 1,200 at 8% for 3 years. Principal is:
ExplanationP = (100 × 1200)/(8 × 3) = Rs. 5,000. -
Q2 Easy
Find principal if SI = Rs. 900 at 6% for 5 years.
ExplanationP = 90000/30 = Rs. 3,000. -
Q3 Medium
SI = Rs. 1,800 at 9% for 4 years. Principal equals:
ExplanationP = 180000/36 = Rs. 5,000. -
Q4 Easy
At 5% for 5 years, SI is Rs. 750. Principal is:
ExplanationP = 75000/25 = Rs. 3,000. -
Q5 Easy
Amount is Rs. 5,600 and SI is Rs. 600. Principal is:
ExplanationP = Amount − SI = 5600 − 600 = Rs. 5,000. -
Q6 Medium
SI = Rs. 2,400 at 12% for 2 years. Find P.
ExplanationP = 240000/24 = Rs. 10,000. -
Q7 Easy
At 10% for 4 years, SI is Rs. 2,000. Principal is:
ExplanationP = 200000/40 = Rs. 5,000.
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Q8 Medium
SI = Rs. 450 at 3% for 5 years. Principal is:
ExplanationP = 45000/15 = Rs. 3,000. -
Q9 Medium
SI = Rs. 1,620 at 6% for 3 years. Principal is:
ExplanationP = 162000/18 = Rs. 9,000. -
Q10 Hard
SI = Rs. 880 at 8% for 2.5 years. Principal is:
ExplanationP = 88000/20 = Rs. 4,400. -
Q11 Hard
Amount is Rs. 6,960 at 8% for 2 years. Principal is:
ExplanationP = 6960/1.16 = Rs. 6,000. -
Q12 Medium
At 15% for 2 years, SI is Rs. 1,500. Principal is:
ExplanationP = 150000/30 = Rs. 5,000. -
Q13 Easy
SI = Rs. 1,000 at 10% for 5 years. Principal is:
ExplanationP = 100000/50 = Rs. 2,000. -
Q14 Easy
SI = Rs. 1,440 at 12% for 2 years. Principal is:
ExplanationP = 144000/24 = Rs. 6,000.
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DS1 Easy
What is the principal?
Statement ISimple interest is Rs. 1,200 at 8% for 3 years.
Statement IIThe rate is 8% per annum.
ExplanationStatement I alone gives P = Rs. 5,000. -
DS2 Medium
What is the principal?
Statement IAmount after 5 years is Rs. 3,750.
Statement IIRate is 5% and time is 5 years.
ExplanationTogether: P = 100 × 3750/(100 + 25) = Rs. 3,000.
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DS3 Easy
What is the principal?
Statement ISI is Rs. 900.
Statement IIRate is 6% and time is 5 years.
ExplanationNeed SI, R and T together. P = Rs. 3,000. -
DS4 Medium
Is the principal greater than Rs. 5,000?
Statement ISI is Rs. 1,800 at 9% for 4 years.
Statement IIRate is 9% per annum.
ExplanationStatement I: P = Rs. 5,000, so it is not greater than Rs. 5,000.