Help with a word problem (ratios)?

Question

On my Yahoo email account, for every 20 emails I receive, 4 are spam. I only look at 2 out of every 17 spam emails that I receive. If I looked at 10 spam emails last month, how many total emails did I receive on my Yahoo account?

Answer 1

We are given that for every 20 messages, 4, or 25%, are spam.

 

Of the spam, only 2 of 17, or 11.765% are viewed.

 

So, if 10 are viewed, then we can figure the original number by

 

10 ÷ 0.11765 ÷ 0.25 = 340

 

Proof: 340 x 0.11765 x 0.25 = 10