5.Problems from Planting Tree

A tree is planted at every 10 metres along a stretch of road. Ifthe stretch of road is

150 m long and the trees are planted at opposite ends of the road, how many trees are there?

Answer explanation

number of intervals = 150 m ÷ 10 m = 15

Since the trees are planted at opposite ends ofthe road, 15 ÷ 1= 16

there are 16 trees.

In a building, there are 8 steps in the staircase leading from one storey to another. How many steps are there from the second to the tenth storey in that building? (Assume the number of steps in each staircase is the same.)

Answer explanation

We must first figure out the number of intervals from the second to the

tenth storey. 10-2= 8

There are 8 intervals from the second storey to the tenth storey. 8 intervals × 8 steps = 64

There are 64 steps from the second storey to the tenth storey in that building.

There are 50 lamp posts along a stretch of road with lamp posts placed at opposite ends of the road. If each lamp post is 2 m away from another, how long is the road

Answer explanation

number of intervals = number of l a m p posts - 1 = 50- 1= 49

49 × 2 m = 98 m

The road is 98 m

long.

There are 21 trees planted along the road divider with trees planted at opposite ends. The trees are planted at

regular intervals of 2 m. If some lamp posts are to be placed along the opposite side of the road at regular intervals of 10 m, how many lamp posts are required on the opposite side of the road iflamp posts are placed at opposite ends of the road?

Answer explanation

number of intervals = number of trees - 1 = 21 - 1= 20

20 × 2 m = 40 m

The road is 40 m long. 40 m ÷ 10 m= 4

Lamp posts are placed along the opposite side of the road at 4 regular intervals. number of lamp posts = 4 +1= 5

5 lamp posts are required at the opposite side of the road.

The stretch of road leading to Cindy's house is to be planted with some trees at

regular intervals of 15 m, and trees are planted at opposite ends of the road. If the road is 900 m long, how many trees are to be planted along that stretch of road?

Answer explanation

n u m b e r o f i n t e r v a l s = 9 0 0 m ÷ 15 m = 6 0

60 +1=61

61 trees are to be planted along that stretch of road.

Pine trees are planted at regular intervals of 5 m along a stretch of road with pine trees planted at opposite ends of the road. If the road is 150 m long, how many pine trees are needed to be planted along the road?

Answer explanation

number of intervals = 150 m ÷ 5 m= 30 30 +1= 31

31 pine trees are needed to be planted along the road.

Lamp posts are placed at regular intervals of 30 m along a 1800-metre road. If the

lamp posts are placed at opposite ends of the road, how many lamp posts are placed along the road?

Answer explanation

number of intervals = 1800 m ÷30 m = 60 60 +1= 61

61 lamp posts are placed along the road

12 pupils stand in a queue. If 4 pots of flowers are placed between every 2 pupils, how many pots of flowers are there altogether?

Answer explanation

number of intervals

= number of pupils - 1

= 12-1

= 1

4 × 11 = 44

There are 44 pots offlowers altogether.

Cindy and Maurice stayed on the fifth and sixth floors of an apartment respectively. If Cindy walked 80 steps up the staircase from the ground floor to her house, how

many steps did Maurice walk from the ground floor to her house? (Assume the number of steps in each staircase is the same.)

Answer explanation

number of staircases from the ground floor to the fifth floor = 5- 1= 4

80 steps ÷4=20 steps

There were 20 steps in each staircase

number of staircases from the ground floor to the sixth floor = 6- 1= 5

5 × 20 steps = 100 steps

Maurice walked 100 steps from the ground floor

to her house.

Trees are planted at regular intervals along a road. If Benny takes 10 min to walk from the first tree to the sixth tree, how long does it take for him to walk to the

fifteenth tree? (Assume

Benny walks at a constant rate.)

Answer explanation

number of intervals from the first tree to the sixth 14 tree

=6- 1

=5

10÷ 5= 2

Benny takes 2 min to walk from one tree to another.

number of intervals from the first tree to the fifteenth tree

= 15 - 1

= 14

2 × 14 = 28

It takes him 28 min to walk to the fifteenth tree