Shortcut Trick
Let Ashish's initial share be A and Ketan's initial share be K.
Time for Ashish = 24 − 13 = 11 years | Time for Ketan = 24 − 14 = 10 years.
Ratio of their shares K / A = (1 + R/100)(11 − 10) = (1 + 4/100)1 = 104/100 = 26/25.
Ketan's share = 26 parts out of total (26 + 25) parts = 26/51 × 25500 = 26 × 500 = 13000.
∴ The correct answer is ₹13000.
Alternate Method
Given:
Total money with Pramod = ₹25500
Age of Ashish = 13 years, Age of Ketan = 14 years
Target Age for receiving money = 24 years
Rate of Compound Interest (R) = 4% annually
Formula Used:
Amount (A) = P(1 + R/100)T
Ashish (13 yrs)
Ketan (14 yrs)
Amount at Age 24
T = 11 yrs @ 4%
T = 10 yrs @ 4%
Calculations:
⇒ Time for Ashish (T1) = 24 − 13 = 11 years
⇒ Time for Ketan (T2) = 24 − 14 = 10 years
⇒ Let Ashish's initial share be P1 and Ketan's initial share be P2.
⇒ Amount received by Ashish = P1(1 + 4/100)11
⇒ Amount received by Ketan = P2(1 + 4/100)10
⇒ Since both receive the same amount at age 24:
⇒ P1(104/100)11 = P2(104/100)10
⇒ P2 / P1 = (104/100)11 − 10 = 104/100 = 26/25
⇒ Ratio of Ketan's share to Ashish's share = 26 : 25
⇒ Sum of ratio parts = 26 + 25 = 51 parts
⇒ Total money = 51 parts = ₹25500
⇒ 1 part = 25500 ÷ 51 = 500
⇒ Ketan's share (P2) = 26 × 500 = ₹13000
∴ The correct answer is ₹13000.
Additional Information
Division of Amount with Equal Maturity
When a given sum is divided into two parts P1 and P2 such that their amounts are equal after t1 and t2 years respectively at R% compound interest, the ratio of their principal amounts is given by P1 / P2 = (1 + R/100)t2 − t1.
Compound Interest Formula
A = P(1 + R/100)T, where A is the final amount, P is the initial principal, R is the annual interest rate, and T is the time in years.
Simple vs Compound Interest
For the first compounding period, SI and CI are equal. For subsequent periods, CI is always greater than SI as interest is earned on the previously accumulated interest.