Lamp posts were located at an equal distance of 21 m apart from one another, starting from the beginning of the road. Between every 2 lamp posts, there were 2 plants, planted 7 m apart.
- What was the distance between the first plant and the 4th plant?
- What was the distance between the fourth plant and the eighth plant?
- Given that the stretch of road was 161 m, how many plants were there?
Lamp post ↔ plant ↔ plant ↔ Lamp post ↔ plant ↔ plant ↔ Lamp post ↔ plant ↔ plant ↔ Lamp post
(a)
Length of each gap
= 21 ÷ 3
= 7
Distance between first and 4th plant
= 4 intervals
= 4 x 7
= 28 m
(b)
Distance between fourth and eighth plant
= 6 intervals
= 6 x 7
= 42 m
(c)
Distance between 2 lamp posts = 21 m
Number of sets of 21 m
= 161 ÷ 21
= 7 r 14
Number of plants at a distance of 14 m
= 14 ÷ 7
= 2
Number of plants
= 7 x 2 + 2
= 16
Answer(s): (a) 28 m; (b) 42 m; (c) 16