Question

If the difference between the simple interest on a certain principal for time period of 3 years and simple interest on the same principal for 4 years is 42. Find the principal if rate of interest
is 5% p.a.

Answer 1

Answer:

Let the sum be Rs. x

According to problem,

⇒ x × 6 × (7/100) – x × 3 × (10/100) = 540

⇒ 0.42x – 0.3x = 540

⇒ x = 4500

∴ The sum = Rs. 4500

Alternate Method

Rate difference = (7% × 6) - (10% × 3) = 42% - 30% = 12%

∴ Interest = 12% of Sum

⇒ 540 = Sum × (12/100)

⇒ Sum = 540 × (100/12) = 4500