the ratio of the number of cars

Question

The ratio of the number of cars to vans in a parking lot is 8:3 and the ratio of the number of motorbikes to vans is 2:5. If there are 15 motorbikes, find the number of cars.

Answer 1

cars/vans=c/v=8/3

motorbikes/vans= m/v=2/5

m=15

find c = number of cars

15/v=2/5

v= 75/2= 37.5 vans

c/(75/2)=8/3

2c/75 =8/3

c/75=4/3

c/25=4

c=100 cars

check the answer

c/v=8/3

100/37.5=8/3

cross multiply

300= 300

m/v=2/5

15/37.5=2/5

cross multiply

75=75

while that 37 1/2 vans is somewhat peculiar, it could be interpreted as an average over time