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Fast food. If four out of five doctors prefer fast food, then at a convention of 445 doctors, how many prefer fast food?

The answer is 356 doctors prefer fast food.

If you cross multiply, it will help you solve this problem. Sorry about the periods, it's the only way I could make this look right. Just ignore them, please.

4......n

_..X.._

5.....445

4 x 445 = 1780

1780 / 5 = 356

n = 356

Let x doctors prefer fast food. Then we set up a proportion as

4: 5 = x: 445

Now, 5 * x = 4 * 445

x = 4 * 445/5 = 89 * 4 = 356

356 doctors prefer fast food.

Multiply the proportion by the number of doctors

So

4 out of 5 doctors is a proportion of 4/5

So 4/5 x 445 = 356

4 out of 5 doctors prefer fast food

? out of 445 doctors prefer fast food

4/5 x 445 = 4 x 89 = 356