Question

If a principal is getting doubled after 4 years, then calculate the rate of interest. 

Answer 1

Let the principal P = Rs 100 

Given it is doubled after 4 years 

i.e. Time n = 4 years 

After 4 years A = Rs 200

∴ A = P + I 

A – P = I 

200 – 100 = I 

After 4 years interest I = 100 

I = \(\frac{pnr}{100}\)

⇒ 100 = \(\frac{100\times4\times\,r}{100}\) 

4r = 100 

⇒ r = 25 % 

Rate of interest r = 25 %