SOLUTION: here are 42 pupils in a class 3\4 of the boys travel by bus an 2\3 of the girls travel to school by bus.the total number of pupils that travel by bus is 30.how many boys are th

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: here are 42 pupils in a class 3\4 of the boys travel by bus an 2\3 of the girls travel to school by bus.the total number of pupils that travel by bus is 30.how many boys are th      Log On


   



Question 703194:
here are 42 pupils in a class 3\4 of the boys travel by bus an 2\3 of the girls travel to school by bus.the total number of pupils that travel by bus is 30.how many boys are there in the class?

Answer by checkley79(3341) About Me  (Show Source):
You can put this solution on YOUR website!
B+G=42
B=42-G
3B/4+2G/3=30
3(42-G)/4+2G/3=30
(126-3G)/4+2G/3=30
[3(126-3G)+4(2G)]/3*4=30
[378-9G+8G]/12=30
-G+378=360
-G=360-378
-G=-18
G=18 THE NUMBER OF GIRLS IN THE CLASS.
B+18=42
B=42-18
B=24 THE NUMBER OF BOYS IN THE CLASS.
PROOF:
3/4*24+2/3*18=30
18+12=30
30=30