What is the approximate percentage decrease in the number of boys in School D in the year 2008 as compared to that in the previous year ?

Answer: Option A

Number of boys in School D in 2007
= 6.4 × 100
= 640
Number of boys in School D in 2008
= 5.3 ×100
= 530
$$\begin{array}{rl}& \text{Decrease }\%\\ & =\left(\frac{110}{640}\times 100\right)\%\\ & =\frac{275}{16}\%\\ & =17.1\%\\ & \approx 17\%\end{array}$$