Question

In how many years will a sum of 1600rs amount to 1852.20 at 5% per annum compound interest

Answer 1

Answer:

First we will find INTEREST

COMES= 1852.20-1600

= 252.20

FIND TIME= SI*100/ P* R

=25220/1600*5

3 yrs

Answer 2

Answer:

3 years

Step-by-step explanation:

compounded amount  = principle ( 1 + rate of return ) ^ time

1852.20 = 1600 [ 1 + (5*100)] ^ time

1852.20 = 1600 ( 1 + 0.05) ^ time

1852.20 / 1600  =  1.05  ^  time

1.157625  = 1.05 ^ time

1.157625 = 1.05³ ( 1.05 * 1.05 * 1.05 = 1.157625 )

or easy but lengthy way

Interest after first year

P * R * T = 1600 * (5/100) * 1 = 80 rs

principle of second year will be 1600 + 80 = 1680

Interest after second year

P * R * T = 1680 * (5/100) * 1 = 84 rs

principle of third year will be 1680 + 84 = 1764

Interest after third year

P * R * T = 1764 * (5/100) * 1 = 88.2 rs

principle after third year will be 1764 + 88.2 = 1852.2

it took 3 years on compound interest