Question

A fence will be built to enclose a 100-m by 70-m field. It will need a post at each corner and one every 5 m. How many posts are needed?

Answer 1

The answer is 68.

Field had shape of rectangle since has difference in length and width. The perimeter of rectangle can be expressed as:
P = 2 × (a + b)

If:
a = 100 m
b = 70 m
Then
P = 2 × (100 m + 70 m)
P = 2 × 170 m
P = 340 m.

If posts are on every 5 m, the number of needed posts is:
340 m ÷ 5 m = 68.
Thus, 68 posts are needed for the fence.