
Shortcut Trick
Difference in their investment time = 19 − 18 = 1 year.
Ratio of their initial investments (Ajay : Prakash) = (1 + 4/100)1 = 104/100 = 26 : 25.
Total ratio parts = 26 + 25 = 51 parts → ₹1224.
Value of 1 part = 1224 ÷ 51 = ₹24.
Prakash's share = 25 parts = 25 × 24 = ₹600.
∴ The correct answer is ₹600.

Alternate Method
Given:
Total amount distributed = ₹1224
Rate of interest (R) = 4% compounded annually
Time for Ajay (T1) = 18 years
Time for Prakash (T2) = 19 years
Formula Used:
Amount in Compound Interest: A = P(1 + R/100)T
Ajay's Principal (A)
18 years @ 4%
Prakash's Principal (P)
19 years @ 4%
Equal Amount
Equal Amount
=
Ratio A : P = 26 : 25 (Total ₹1224)
Calculations:
⇒ Let Ajay's share be A and Prakash's share be P.
⇒ Amount received by Ajay after 18 years = A(1 + 4/100)18
⇒ Amount received by Prakash after 19 years = P(1 + 4/100)19
⇒ Both final amounts are equal, so:
⇒ A(1 + 4/100)18 = P(1 + 4/100)19
⇒ A / P = (1 + 4/100)19 − 18
⇒ A / P = (1 + 1/25)1 = 26 / 25
⇒ The ratio of their initial shares is A : P = 26 : 25.
⇒ Sum of their ratio parts = 26 + 25 = 51 parts.
⇒ 51 parts represent the total sum = ₹1224.
⇒ 1 part = 1224 ÷ 51 = ₹24.
⇒ Prakash's share (P) = 25 parts = 25 × 24 = ₹600.
∴ The correct answer is ₹600.

Additional Information
Compound Interest Formula
The final amount after T years at R% compound interest is given by A = P(1 + R/100)T.
Division of Sum in Compound Interest
When a sum is divided into two parts P1 and P2 such that their amounts become equal after T1 and T2 years, the ratio of their original shares is P1 / P2 = (1 + R/100)T<sub>2</sub> − T<sub>1</sub>.
Time & Investment Relationship
The person whose money is invested for a lesser time period must always receive a larger portion of the initial principal so that both investments can grow to reach exactly the same final amount.