If the simple interest for 6 years be equal to 30% of the principal, i

1.	If the simple interest for 6 years be equal to 30% of the principal, it will be equal to the principal after (a) 10 years (b) 20 years (c) 22 years (d) 30 years
Answer» (b) 20 years. Let the principal = Rs x and rate of interest = R% p.a. Then, S.I. = 30% of Rs x = \(\frac{30}{100}\times x\) ∴ \(\frac{x\times{R}\times6}{100} = \) \(\frac{30}{100}\times x\) ⇒ R = \(\frac{30}{6}=\) 5 % p.a. Let the time in which the principal is equal to simple interest be t years, then \(\frac{x\times{5}\times{t}}{100} = x\) ⇒ t = \(\frac{100}{5}years\) = 20 years.

If the simple interest for 6 years be equal to 30% of the principal, it will be equal to the principal after (a) 10 years (b) 20 years (c) 22 years (d) 30 years

Answer»

(b) 20 years.

Let the principal = Rs x and rate of interest = R% p.a.

Then, S.I. = 30% of Rs x = \(\frac{30}{100}\times x\)

∴ \(\frac{x\times{R}\times6}{100} = \) \(\frac{30}{100}\times x\)

⇒ R = \(\frac{30}{6}=\) 5 % p.a.

Let the time in which the principal is equal to simple interest be t years, then

\(\frac{x\times{5}\times{t}}{100} = x\) ⇒ t = \(\frac{100}{5}years\) = 20 years.