question_answer

Aniket deposited two parts of a sum of Rs. 25000 in different banks at the rate of 15% per annum and 18% per annum respective. In one year got Rs.4050 as the total interest. What was the amount deposited at the rate of 18% per annum?

A)  Rs. 10000                    

B)  Rs.18000         

C)         Rs.15000         

D)         Rs.12000         

E)  Rs.16000

Correct Answer: A

Solution :

Logical approach (By alligation method) Total interest = 4050 Average rate of interest \[=\frac{4050}{25000}\times 100=16.2%\] Now,  Now, at the rate of 18% amount, \[=\frac{25000}{5}\times 2=Rs.10000\] Another method: Let the amount invested at the rate 15% be Rs. x.                Then, at the rate of 18% the amount invested will be Rs. (25000 - x). Now \[=\frac{(25000-x)\times 18\times 1}{100}+\frac{x\times 15\times 1}{100}=4050\] \[\Rightarrow 25000\times 18-18x+15x=4050\times 100\] \[\Rightarrow 3x=25000\times 18-4050\times 100\] \[=450000-405000=45000\] \[\therefore x=15000\] \[\therefore \]Amount invested at the rate of 18% = 25000 - 15000 = Rs. 10000