
Shortcut Trick
For compound interest questions where final amounts are equal, the ratio of principal invested is inversely proportional to the respective multiplying factors for the time difference.
Time difference = 18 − 17 = 1 year.
Ratio of Anand's share to Anil's share = (1 + 4/100)1 = 104/100 = 26/25.
Total parts = 26 + 25 = 51 parts.
Anil's share (25 parts) = (25 ÷ 51) × 1224 = 25 × 24 = ₹600.
∴ The correct answer is ₹600.

Alternate Method
Given:
Total amount distributed = ₹1224
Rate of Interest (R) = 4% compounded annually
Time for Anand (t1) = 17 years
Time for Anil (t2) = 18 years
Formula Used:
Amount in Compound Interest, A = P(1 + R/100)n
Total: ₹1224
Anand (P1): 17 years
Ratio: 26 parts
Anil (P2): 18 years
Ratio: 25 parts
Equal Amount (A)
Calculations:
⇒ Let the principal sum given to Anand be P1 and to Anil be P2.
⇒ P1(1 + 4/100)17 = P2(1 + 4/100)18
⇒ P1 / P2 = (1 + 4/100)18 − 17
⇒ P1 / P2 = (1 + 1/25)1
⇒ P1 / P2 = 26 / 25
⇒ The sum of ₹1224 is divided in the ratio of 26 : 25.
⇒ Total ratio parts = 26 + 25 = 51 parts.
⇒ 51 parts = ₹1224
⇒ 1 part = 1224 ÷ 51 = 24
⇒ Anil's principal share (P2) = 25 parts = 25 × 24 = 600
∴ The correct answer is ₹600.

Additional Information
Compound Interest Formula
The amount after n years at r% compound interest per annum is derived using A = P(1 + r/100)n.
Equal Amount Rule
When a sum is split into two parts P1 and P2 for n1 and n2 years respectively such that their end amounts are exactly equal, the initial parts hold the relation P1 / P2 = (1 + r/100)n2 − n1.
SI vs CI Difference
The direct difference between CI and SI on the same principal is D = P(r/100)2 for 2 years, and D = P(r/100)2(3 + r/100) for 3 years.