If Y=39 when X=26 what is X when Y=21?

Answer 1

Set up equivalent ratios:

26/39 = x/21

2/3 = x/21

Solve for x.

Answer 2

Hello Madelyn. There are two ways to solve this problem. The first way is to set up a proportion. The proportion would go as follows:

X1 =X2

Y1 Y2

Substituting the values given for x and y gives us:

26 = X

39 21

We can then cross multiply and solve for x:

546= 39x

39 39

x= 14

The second method we can use is the formula that directly connects x and y. That formula is y=kx where k is the constant of proportionality. We can use the first x and y values (26 and 39) to find the constant of proportionality (k). Doing so yields:

y=kx

39= 26k

26 26

k=1.5

We can now use the second y value (21) and the constant of proportionality (1.5) to solve for x using the same formula as before.

Doing so yields:

y=kx

21= 1.5x

1.5 1.5

x=14