At what rate of compound interest does a sum of money become?

At what rate per cent compound interest, does a sum of money become 1.44 times of itself in 2 years ?

Let Principal = Rs. yThen Amount= Rs 1.44y

n= 2 years

∴ Amount = `"P"( 1 + "r"/100 )^n`

⇒ 1.44y  = `y( 1 + r/100)^2`

⇒ `[1.44y]/y = ( 1 + r/100)^2`

⇒ `36/25 = ( 1 + r/100)^2`

⇒ `( 6/5 )^2 = ( 1 + r/100)^2`

On comparing,
`6/5 = 1 + r/100`

On solving, we get
 r = 20 % 

Concept: Concept of Compound Interest - Inverse Formula

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