Suppose y is directly proportional to x and that y = 40 when x=5.
Complete parts (a)and(b).
Find the constant of proportional k.
k=
(b)use y=ky to find y when x=9
y=
I just did this
http://www.jiskha.com/display.cgi?id=1438462215
To find the constant of proportionality, k, you can use the given information that y is directly proportional to x. This means that the ratio of y to x is always the same. In symbolic terms, y ∝ x.
In this case, you are given that y = 40 when x = 5. To find k, you can set up a proportion using these values:
y/x = k
Substituting the given values:
40 / 5 = k
Simplifying the equation:
8 = k
Therefore, the constant of proportionality, k, is 8.
To find y when x = 9, you can use the equation y = kx with the value of k you found earlier:
y = 8 * 9
Simplifying the equation:
y = 72
Therefore, y is equal to 72 when x is 9.