One third of a certain sum is lend out at 3% rate of interest, one fourth of the sum is lend out at 6% rate of interest and the rest is lend out at 8% rate of interest. The simple interest on the whole sum for 2 years is ₹420. Find the principal.

₹ 3600

Let the Principal = Rs.1200

i) Interest on one third part = 1200 × \(\frac{1}{3}\) × 3% = Rs. 12

ii) Interest on one forth part = 1200 × \(\frac{1}{4}\) × 6% = Rs. 18

iii) Interest on rest part = 500 × 8% = Rs. 40

Total interest in one year = 12 + 18 + 40 = Rs. 70

Total interest in two year = Rs. 140

ATQ,

140 unit = 420

1 unit = 3

Principal  = 1200 unit = 1200 × 3 = Rs. 3600