Length of the hall = 20 m,
Breadth of hall = 15 m,
Area of hall = L x B = 20 x 15 = 300 m2
Length of hall with verandah = 20 + 2.5 + 2.5 = 25 m,
Breadth of hall with verandah = 15 + 2.5 + 2.5 = 20 m,
Area of hall with verandah = 25 x 20 = 500 m2
Area of verandah = area of hall with verandah - area of hall
= 500 - 300 = 200 m2
Cost of flooring the verandah is Rs. 3.50 per square meter.
So, the cost of flooring the entire verandah = 3.50 * 200 = Rs. 700