SOLUTION: The volume of a car, V, is directly proportional to the square of its length, l. Calculate the percentage increase in V when l is doubled.

Question 550154: The volume of a car, V, is directly proportional to the square of its length, l. Calculate the percentage increase in V when l is doubled.
Answer by TutorDelphia(193) (Show Source): You can put this solution on YOUR website!
direct proportion's formula is y=kx. In this case y=V and x=length squared

Let's say the length was 10 and k was 1

v=1*400
400 is a 300% increase using the formula new minus old over old or (400-100)/100=3=300%
Now let's do the general case. Percent increase is new minus old over old

new minus old over old:

The k and l^2 cancel out and we are left with 3 which is equal to 300%

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