Question

What is the interest of Rs. 1080 after 4 years at the rate of Rs. 10%?. After how many years is the interest be same for Rs. 900 at the rate of 12% interest?​

Answer 1

We know that

Simple Interest = PTR/100

=> Simple Interest = (1080×4×10)/100

=> Simple Interest = 108×4

=> Simple Interest = Rs. 432

Let the required time be T years

Given Principal = Rs. 900

Rate of interest = 12%

Given that Bothe interests are same.

=> 432 = (900×T×12)/100

=> 432 = 9×T×12

=> 432 = 108 ×T

=> 432/108 = T

=> T = 432/108

=> T = 4 years

Answer :-

• The required time is 4 Years

Answer 2

Answer:

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given

Interest on Rs. 1080 for 4 years at 5% = 1080 * 0.05 * 4 = Rs. 216

Let the no. of years = t for the first case ( Principle Rs. 1800, rate 3%)

So, we have 1800 * 0.03 * t = 216

Or, t = 216/(1800 * 0.03 ) = 4 years Ans.

Consider Compound interest :

Interest on Rs. 1080 for 4 years at 5% = 1080 * ( 1 + 5/100)^4 - 1080 = Rs.232.75

Let the no. of years = t for the first case ( Principle Rs. 1800, rate 3%)

So, we have 1800 * ( 1 + 3/100)^t - 1800 = 232.75

Or, 1.03^t = (232.75+1800)/1800 = 1.1293

Taking logarithm on both sides, t * log 1.03 = log 1.1293

Or t = log 1.1293/log 1.03 = 4.114 years Ans

Step-by-step explanation:

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