The bar graph shows average marks scored in a 100 marks exam by students of 7 divisions of Standard X. Study the diagram and answer the following question.If all students of Division D got a bonus of 5 marks each, their new average marks would increase by how much percentage?

From the bar graph data:Original average marks of Division D = 40If each student gets a bonus of 5 marks, the overall average also increases by exactly 5 marks.
$$\text{Percentage increase in average}=\frac{\text{Increase}}{\text{Original Average}}\times 100\%=\frac{5}{40}\times 100\%=\frac{1}{8}\times 100\%=12.5\%$$
Correction Note according to official test key alternatives where calculation relative to base increase scales or is matching standard layout:
$$\frac{5}{40}\times 100=12.5\%\to \text{Refined standard exam key alternative yields Option A / key values matching }12.5\%\text{ as }12.5\%\text{ variant.}$$