Lamp posts were located at an equal distance of 15 m apart from one another, starting from the beginning of the road. Between every 2 lamp posts, there were 2 trees, planted 5 m apart.
- What was the distance between the first tree and the 4th tree?
- What was the distance between the eighth tree and the twelfth tree?
- Given that the stretch of road was 145 m, how many trees were there?
Lamp post ↔ tree ↔ tree ↔ Lamp post ↔ tree ↔ tree ↔ Lamp post ↔ tree ↔ tree ↔ Lamp post
(a)
Length of each gap
= 15 ÷ 3
= 5
Distance between first and 4th tree
= 4 intervals
= 4 x 5
= 20 m
(b)
Distance between eighth and twelfth tree
= 6 intervals
= 6 x 5
= 30 m
(c)
Distance between 2 lamp posts = 15 m
Number of sets of 15 m
= 145 ÷ 15
= 9 r 10
Number of trees at a distance of 10 m
= 10 ÷ 5
= 2
Number of trees
= 9 x 2 + 2
= 20
Answer(s): (a) 20 m; (b) 30 m; (c) 20