Question

approximately 9 out of 10 smokers began smoking before the age of 21. In a group of 400 smokers, about how many of them started before they reached their 21st birthday?

Answer 1

360. Divide 400 by 10 and multiply that by 9.

Answer 2

Greetings!

You can create an equation to solve for x:
$9/10=x/400$
Cross Multiply.
$9*400=10*x$
$3600=10x$
Divide both sides by 10.
$(3600)/10=(10x)/10$
The Answer Is:
$360=x$


Out the 400 smokers, approximately 360 of them started smoking before age 21.

Hope this helps.
-Benjamin