A painter needs to cover a triangular region 61 meters by 69

A painter needs to cover a triangular region 61 meters by 69 meters by 72 meters. A can of paint covers 70 square meters. How many cans will be needed?

Solution

a = 61, b = 69, c = 72

semiperimeter, s = (61 + 69 + 72)/2 = 101 m

now area of region = sqrt[s x (s-a) x (s-b) x (s-c)]

= sqrt[101 x 40 x 32 x 29]

= 1936.264445 m²

Number of cans needed = 1936.264445/70 = 27.661

so 28 cans are needed