Question

At what rate of interest per annum, a sum of Rs. 800 will become Rs. 1200 in 10 years?

Answer 1

5 % is the correct answer

You can 1st find the SI by SI = A-P

then use formula for R

R = SI ×100 upon P × T

Answer 2

The answer is 5%

GIVEN

A sum of Rs. 800 will become Rs. 1200 in 10 years.

TO FIND

The rate of interest.

SOLUTION

The above problem can be simply solve as follows;

It is given,

Principal amount = Rs 800

Amount = Rs 1200

Time = 10 years

Let the rate of interest = R

It is known that,

Final Amount = Principal amount + Simple interest.

Formula to calculate simple interest.

SI = (P × R × T) ÷ 100

Putting the values.

SI = (800 × 10× R) ÷ 100

= 80R

Now,

Final Amount = Principal amount + Simple interest.

1200 = 800 + 80R

1200-800 = 80R

400 = 80R

R = 400/80 = 5

Hence, The answer is 5%

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