21 trucks, each with a 2.5-ton payload, are needed to unload a freight train. b find the constant of variation.

2.5-ton payload per truck

Step-by-step explanation:

Given the following equation:

total payload = 2.5-ton payload per truck * number of trucks

it can  be rewritten as:

y = k*x

where y and x are variables and k is the constant of variation. Comparing these two equation, we see that 2.5-ton payload per truck is the constant of variation, and total payload and number of trucks are the directly variated variables, because when the number of trucks  increase, the total payload also increased.

step-by-step explanation:

we are given

since, we have to isolate x on anyone side

so, we can move all x terms on one side

subtract both sides by 2x

add both sides by 9

divide both sides by 4

we get