Question

I need help on this question. Please ?

Answer 1

The answer would be: A. 50

Answer 2

Let original diameter be x
area = $\pi (x/2)^{2}$

After the original diameter has increased by 50%
x = 1.5x
area = $\pi (3x/4)^{2}$

changes in area = $\pi (3x/4)^{2}$ -  $\pi (x/2)^{2}$ 
changes in area = $\pi [(3x/4)^{2} -(x/2)^{2}]$
changes in area = $\pi [9x^2/16 - x^2/4]$
changes in area = $\pi [9x^2/16 - 4x^2/16]$
changes in area = $\pi [5x^2/16]$

Change in area = $\pi [5x^2/16]$ / $\pi (x/2)^{2}$  x 100
Change in area = $[5x^2/16]$ x $[4/x^2]$  x 100
Change in area = 5/4 x 100
Change in area = 125% (Answer D)