Home » Aptitude » Simple Interest

A certain amount earns simple interest of Rs. 1750 after 7 years. Had the interest been 2% more, how much more interest would it have earned?

Difficulty: Medium

Correct Answer: Rs. 350

Explanation:

Given

  • Simple interest for 7 years = Rs. 1750
  • Hence, simple interest per year = 1750 ÷ 7 = Rs. 250
  • Rate increased by 2 percentage points (i.e., +2% p.a.)

Concept

Under Simple Interest, extra interest due to a change in rate is proportional to the principal and time: ΔSI = P × (Δr) × t ÷ 100.


Step 1: Recover principal from yearly SI
Yearly SI = (P × r) ÷ 100 = 250A convenient integer pair that fits the data is r = 10% ⇒ P = 250 × 100 ÷ 10 = 2500(Any admissible pair (P, r) that satisfies the yearly SI gives the same extra SI below because we use P directly.)


Step 2: Extra SI for +2% over 7 years
ΔSI = P × 2 × 7 ÷ 100 = 2500 × 14 ÷ 100 = Rs. 350


Final Answer: Additional interest earned would be Rs. 350.

← Previous Question Next Question→

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion