Question

the number of boys and girls in class are in the ratio 7:5 find the numbers of boys is 8 more than the numbers of girls what is total class strength

Answer 1

Let number of boys are X and number of girls are Y..
X/Y = 7/5
5X = 7Y
X = Y+8
5(Y+8) = 7Y
5Y + 40 = 7Y
2Y = 40
Y = 10
X= Y + 8
X = 18
X+Y= 28

Answer 2

$hi$
let the no. of boys be x and no. of girls be y.

By the 1st given condition ,

$\frac{x}{y} = \frac{7}{5}$

$5x = 7y$

$5x - 7y = 0............(1)$
By the 2nd given condition ,

$x = y + 8$

$x - y = 8..............(2)$

$now....$
[multiply equation no. (2) by 7]
so,

7x - 7y = 56 ..............(3)

[Subtracting equation no. (3) from (1)]

5x - 7y = 0
7x - 7y = 56
__________
-2x = -56
2x = 56
x = 56 / 2
x = 28

Substitute x = 28 in equation no. (2)

x - y = 8
28 - y = 8
28 - 8 = y
y = 20

we get....

x = 28 & y = 20 .
___________________________
Strength of the class :
x + y = 28 + 20 = 48

The strength of the class is 48.

hope this helps ! ! !