Anglo-Chinese School (Primary) P5 SA2 2006 Math Question (Q40)

Lamp posts are placed round a square field measuring 60 m by 60 m. The lamp posts are placed 10 m apart with a post at each corner. How many posts are needed in all?

Solution




1 side of square has

7 lamp posts – 2 corner lamp posts = 5 lamp posts.

4 sides ----- 5 lamp posts x 4 = 20 lamp posts

Total lamp posts ----- 20 lamp posts + 4 corner lampposts = 24 lamp posts

Answer: There are 24 lamp posts in all.