Posted by **mathsmad** on Saturday, September 10, 2011 at 12:28am.

There were 335 children in a hall. 1/4 of the girls and 2/5 of the boys are swimmers. There are 110 swimmers in all. How many boys are there in the hall?

- maths -
**Jai**, Saturday, September 10, 2011 at 3:22am
first we represent unknowns using variables.

let x = number of girls in the hall

since the the total number of children is 335,

let 335 - x = number of boys in the hall

then we set-up the equation. since 1/4 of the girls and 2/5 of the boys are swimmers and their total is 110,

(1/4)*x + (2/5)*(335 - x) = 110

(1/4)*x + 134 - (2/5)*x = 110

(1/4 - 2/5)*x = 110 - 134

(5/20 - 8/20)*x = -24

(-3/20)*x = -24

to get x alone, we multiply both sides by the reciprocal of the numerical coefficient (the number before the variable). thus:

[(-3/20)*x = -24]*(-20/3)

x = 160 (number of girls)

335-x = 175 (number of boys)

hope this helps~ :)

- maths -
**mathsmad**, Saturday, September 10, 2011 at 3:44am
could you pls show me a non- algebra way as i have not learnt algebra yet, tks

- maths -
**MnZsT**, Saturday, September 10, 2011 at 5:21am
1/4 girl + 2/5 boy = 110

3/4 girl + 3/5 boy = 335- 110 =225

3/4 girl + 6/5 boy = 110 X 3 = 330

3/5 boy = 330 - 225 = 105

1/5boy = 105/3 = 35

5/5 boy = 35 X 5 = 175 (answer)

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