Question

# 25 i ont get it :(

Answer 1

4 out of 10 drink enough water.

How many tens are there in the class of 40 ?

Four tens ?
And out of each 10, 4 do it ?

Then wouldn't there be (4 x 4) = 16 in the whole class getting enough water ?  
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Answer 2

$\frac{4}{10} = \frac{x}{40}$
cross multiply 4 x 40. 160
Now divide by 4 
40