The student population of a certain school increased a% from 1995 to 2

Let the number of students initially in 1995 = 100.

Therefore the total number of students in 2015 (80% increase) = \(100 * \frac{(100 + 80)}{100} = 180\)


The total increase = 180 - 100 = 80

Let x be the increase in the number of students in 1995 and 2005 (1st decade)

The increase in the number of students in the second decade = 3x (This has been stated)

Therefore the total increase x + 3x = 80

4x = 80 or x = 20


We have the following (1995) 100. This increased by 20 => (2005) 120. This increased by 3x = 60 => 2015 (180)

We have to calculate the % increase from 120 to 180



%\(Increase = \frac{Difference}{Smaller \space number} * 100 = \frac{180 - 120}{120} * 100 = 50\)%



Option C

Arun Kumar