Question

at which rate of simple interest a sum double in 20 years​

Answer 1

Answer:

Let the principle = x

Time = 20 years

R =?

and Amount A = 2x

We know that,

A = P ( 1 + TR /100)

2x= x ( 1+ 20 R /100)

2x / x = 1+ 20 R /100

2-1 = R / 5

R =5*1=5%

At 5% simple interest, a sum of money doubles itself in 20 years.

Answer 2

A=P+PTR/100

A is amount

P is Principal

R is rate of interest

T is time period in years

given, sum doubles in 20yr i.e,

A=2P,T=20

2P=P+P(20)R/100

2P-P=P(20)R/100

P=P(20)R/100

R=5%