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joel

The ratio of boys to girls in a class is 5:9 if 19 was added to the boys and 4 was added to the girls the ratio will be 9:7  QUESTION how many was the original number of boys and girls in the class?

the ratio of boys to girls in a class is 5:9 if 19 was added to the boys and 4 was added to the girls the ratio will be 9:7  QUESTION how many was the original number of boys and girls in the class?

Posted in Math, asked by joel, 6 years ago. 2559 hits.

-1

let original number of boys be   x
let original number of girls be   y

number of boys/number of boys = x/y = 5/9

therefore, 9x = 5y        ---------------------- equtaion (1)

when 19 boys are added the number of boys become = x+19

when 4  girls are added the number of girls become =  y+4

therefore the new raito becomes,  x+19/y+4 = 9/7

7(x+19) = 9(y+4)
7x+133 = 9y+36
7x+133-36 = 9y

7x+97 = 9y    -------------------- equation(2)

dividing equation (1) & (2)

9x/7x+97 = 5y/9y

9x/7x+97 = 5/9

x = 485/46 = 10.54
since number of boys can not be in decimals so we take as x = 10
now on putting the value of x in equation (1)

9*10 = 5y
y=18

hence the original number of boys in the class is 10 and girls is 18.

priyanka sharma
priyanka sharma - 6 years ago
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-1

Sol ---The ratio of boys to girls in a class is 5:9 . Let the common multiple be  X . Therefore the number of boys and girls wil be 5X and 9X 

          19 was added to the boys and 4 was added to the girls the ratio will be 9:7 .

          then the equation becomes  5X + 19 / 9X + 4 = 9/7

                                               On solving you will get the value of X . therefore the no of boys wil be 5X and 9X .

                          ( In this problem , there is some mistake hence we are getting the answer in fraction , but number of boys and girls cant be in fractions . I have just shown the method to solve the problem .)

amit helekar
amit helekar - 6 years ago
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