If 3 pounds of apples cost $0.90, how much will 10 pounds cost?

First we need to figure out how much 1 pound of apples would cost. This can be done by dividing 90 cents by 3 pounds.

3 pounds / 90 cents = 1 pound / 30 cents

Now since 1 pound of apples is 30 cents or $0.30 (read 30 cents per pound) we can easily find how much 10 pounds of apple would be.

10 pounds * 30 cents / 1 pound

As you can see the pound units will cancel out leaving only the unit cents.

10 * 30 cents / 1 which is just 10 * 30 cents

And that is 300 cents. Which is of course 3 dollars.

$3.00