(b) 1000
Let the total number of students in the school be x.
Then, Number of girls = \(\frac{3x}{7}\)
Number of boys \(\frac{4x}{7}\)
Number of boys below ten years of age = \(\frac14\times\frac{4x}{7}=\frac{x}7\)
Number of girls below ten years of age = \(\frac56\times\frac{3x}{7}=\frac{5x}{14}\)
∴ Total number of students below 10 years of age = \(\frac{x}7+\frac{5x}{14}= \frac{7x}{14}=\frac{x}{2}\)
∴ Total number of students above 10 years of age = \(x-\frac{x}{2}=\frac{x}2\)
Given, \(\frac{x}2\) = 500 ⇒ x = 1000.