00:01
So y varies inversely as x does, and we're told that when y is equal to three, x is equal to 12, and we want to find what y is when x is equal to 40.
00:13
All right, so we can solve this in the following way.
00:19
So y inversely is x, means this is going to be y is equal to k over x, like so, because remember inversely means one over it.
00:32
And k is just our constant.
00:36
But since we don't need to solve for k in this problem, let's multiply each side by x.
00:44
The x is there cancel out.
00:46
Now we'd have x times y is equal to k.
00:51
Now what i'm going to do is label this x1y1, and on the other side i'm going to set this equal to x2 y2 because we know that any pair of x and y should be equal to our constant here.
01:06
So if we look at the values that we have up here, i'll call this one, y1, x1, this will be y2, and x2.
01:20
So now we can just plug those values into this equation here and then solve for y...