quekcc wrote:I think the answer should be 210 boys.jojoberry wrote:Daddy wrote:Hi all,

I have 2 questions to ask.

THANK ALL..

You can explain using model or algebra.

Let me do it in model.

Let the number of girls be 10 x ,

then the number of boys will be 10 x + [90]

After 80% boys and 30% girls left, we have remaining

girls: 7 x

boys: 2 x + 18 Note: 90/10 x 2 = 18

Now girls is double of boys, i.e.

7 x = 2 x + 18 + 2 x + 18

so

3 x = 36

= 12

Number of boys at first = 10 x 12 + 90 = 210 (Ans)

Hi,

Yes, answer sh be

**210**.

(Not 420)

Cheers

**speedmaths**

.