Question

At Billy's school, 80 students come to school by bicycle or by car. Together, the vehicles they arrive to school in have 270 wheels. How many of each are used

Answer 1

x = number of bicycles = 35

y = number of cars = 55

Explanation:

Let

x = number of bicycles

y = number of cars

x + y = 80 (1)

2x + 4y = 270 (2)

From (1)

x = 80 - y

Substitute x = 80 - y into (2)

2x + 4y = 270 (2)

2(80 - y) + 4y = 270

160 - 2y + 4y = 270

- 2y + 4y = 270 - 160

2y = 110

y = 110/2

y = 55

Substitute y = 55 into (1)

x + y = 80 (1)

x + 55 = 80

x = 80 - 55

x = 35

x = number of bicycles = 35

y = number of cars = 55