Question

In a class , one out of every 6 students fails.if there are 42 students in the class , how many pass?
2. For every 12 mangoes that I buy, 3 turn out to be rotten. At this rate , how many rotten mangoes will I have if I buy 100 mangoes. ?

Answer 1

1) One out of 6 students fail
That means, 5 out of 6 students pass
Passed students = $\frac{5}{6} * 42$ = 35
35 students pass

2) 3 out of 12 mangoes are rotten. 
Rotten mangoes = $\frac{3}{12} * 100$ = 25
25 mangoes are rotten. 

Answer 2

1. one out of 6 student fail I.e fail ratio1/6
                                            pass ratio=1-1/6=5/6
     Out of 42 student  (5/6)*42=35 student pass.

2.  In 12 mangoes 3 are rotten.
     % of rotten mangoes= 3*100/12=25%
     For 100 mangoes no. of rotten mangoes will be=(25/100)*10=25