Question

x and y vary inversely, and y = 2 when x = 5. Find y when x = 3.

Answer 1

If x and y varies inversely, then xy = k, where k is a constant.

Answer 2

let's find k.

we are told that y = 2 and x = 5,

so substitute these two values, you get (2)(5) = k
so k =10.

agree?

Answer 3

yes that is what I got. But after that im lost in what to do.

Answer 4

I'm not done.

Answer 5

ok

Answer 6

Now that we know that k = 10,

our equation is xy = 10.

So now let's answer the question...find y when x = 3.

Well, let's substitute x = 3 into our equation of xy = 10,

we get 3y = 10, so y = 3 1/3.

Makes sense?

Answer 7

I think so. Is the answer 3 1/3?

Answer 8

yes.

Answer 9

ok I get it! Thanks so much for your help! :)

Answer 10

Whats important, is that whenever two quantities, say x and y, vary inversely, then the two quantities, say x and y, must satisfy the equation xy = k.

Then you dind k.

So you have your full equation xy = k

Then you can find anything by substitution.

Answer 11

You're welcome.