The total number of cars that can be washed by 30 volunteers in 3 hours is 180 and this can be determined by using the unitary method.
Given :
20 volunteers can wash 100 cars in 2.5 hours.
The unitary method can be used in order to evaluate the constant of variation and the total number of cars can 30 volunteers wash in 3 hours.
According to the given data, if 20 volunteers can wash 100 cars in 2.5 hours then 1 volunteer can wash 100 cars in:
[tex]\rm =2.5 \times 20 \; hours[/tex]
= 50 hours
If in 50 hours 1 volunteer can wash 100 cars then in 1 hour 1 volunteer can be washed:
[tex]=\dfrac{100}{50}[/tex]
= 2 cars in one hour
If in 1 hour 2 cars can be washed by one volunteer then in 3 hours 1 volunteer can be wash:
= 2 [tex]\times[/tex] 3
= 6 cars
Noe, if 1 volunteer can wash 6 cars in 3 hours then 30 volunteers can wash:
[tex]= 30\times 6[/tex]
= 180 cars
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