Question

A tree increases annually by $\frac{1}{8}$ th of its height, By how much will it increase after 2 years, if it stands today 64 cm high?

• A. $72$ cm
• B. $74$ cm
• C. $75$ cm
• D. $81$ cm

Answer 1

The correct option is D $81$ cm

Let the original height of the tree$=x$ cm.

We know that

final height=original height${\times (1+rate)}^{time}$

Here the rate is$\frac{1}{8}$, time=2yrs, original height=64cm.

Then the height after 2yrs.=$64{\times (1+\frac{1}{8})cm}^2=\frac{64\times 81}{64}cm=81cm.$