A sum at a certain rate of simple interest becomes Rs 14880 fter 3 years and Rs 16800 after 5 years. Find the simple interest on the same sum at 10% per annum for 4 years (in Rs).
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 4800
Given :
Amount in 3 years = Rs 14880
Amount in 5 years = Rs 16800
Rate = 10%
Formula used :
Simple interest = (P × R × T)/100 ----- (1)
Amount = Principal + Simple interest
Where P = Principal, R = Rate and T = time period
Calculations :
Amount in 3 years = SI + P
Using equation (1)
⇒ 14880 = P + ((P × R × 3)/100) ----- (2)
Amount in 5 years = SI + P
⇒ 16800 = P + ((P × R × 5)/100) ----- (3)
Subtracting equation (2) from (3)
⇒ 16800 - 14880 = 2PR/100
⇒ 1920 = 2PR/100
⇒ PR = 96000 ----- (4)
Using equation (4) in equation (3)
⇒ 16800 = P + (96000 × 5)/100
⇒ 16800 = P + (4800)
⇒ P = 16800 - 4800
⇒ P = 12000
Using formula (1)
⇒ (12000 × 10 × 4)/100
⇒ Rs 4800