Question

at what to rate of the simple interest will sum of money will double itself in 20 years

Answer 1

Let the principle=100

Amount =200

Si=100

Rate=si*100/p*t=100*100/100*25=4percent

Answer 2

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Here is your answer
Let the principal is P
and Rate of interest is r %
T = 20 years
A = 2p
Therefore
SI = A - P
= 2p - p
= p
As we know the formula
SI = PRT/100
$p = \frac{p \times r \times 20}{100} \\ r = \frac{p \times 100}{20 \times p} \\ r = 5\%$
Therefore Rate of interest is 5 %

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