Question

the ratio of the number of boys to the number of girls in a school of 560 pupils 5:3 if 10 new boys are admitted find how many new girls may be admitted so that ratio of the number of boys to the number if girls may change to 3:2​

Answer 1

Answer:

(i) It is given that

Mixture of milk to water =45 litres

Ratio of milk to water =13:2

Sum of ratio =13+2=15

Here the quantity of milk =(45×13)/15=39 litres

Quantity of water =45×2/15=6 litres

Consider x litre of water to be added, then water =(6+x) litres

Here the new ratio =3:1

39:(6+x)=3:1

We can write it as

(6+x)

39

=

1

3

By cross multiplication

39=18+3x

3x=39–18=21

x=21/3=7 litres

Hence, 7 litres of water is to be added to the mixture.

(ii) It is given that

Ratio between boys and girls =5:3

Number of pupils =560

So the sum of ratios =5+3=8

We know that

Number of boys =

8

5

×560=350

Number of girls =

8

3

×560=210