If each edge of a cube is increased by 25%, then the percentage increase in its surface area is?

Question: If each edge of a cube is increased by 25%, then the percentage increase in its surface area is?

Solution:
Let the original edge = a
Then, the surafce area = 6a²
New edge = 125a/100 = 5a/4
New surafce area = 6 × (5a/4)² = 75a²/8
Increase in surface area = (75a²/8 - 6a²) = 27a²/8
The percentage increase in its surface area = (27a² × 1/6a² × 100)% = 56.25%