Question

Suppose you have ₹12000 to save. You have to save some amount at 10% and the rest at 15%.how much should be saved at each rate to yield 12% on the total amount saved.

Answer 1

Let sum of the amount = 12000 Rs
x + y = 12000
Interest: 0.10x + 0.15y = 12 % on the total amount ---------(1)
y = 12000 - x
He get 12% on the total amount = 12000 $\times$ $\frac{12}{100}$ = Rs. 1440
Substitute y in equ (1)
0.10x + 0.15(12000-x) = 1440
10x + 15(12000-x) = 144000
- 5x = 144000 -15 $\times$ 12000 = -36000
5x = 36000
x = 7200 Rs (amount invested at 10%)
12000 - x = 4800 Rs (amount invested at 15%)