Help me work out my sons maths challenges please

[notnagging]

My ds loves maths but I am no good at it. He set me the following that took me ages to work out.
There are 2 brothers & 2 sisters. The years between the boys is 2, the same as the girls. The youngest boy is double the age of the oldest girl. There ages add up to 42 altogether. How old is the youngest child?

How did you work it out & how long did it take you?

[noblegiraffe]

I called the youngest boy b and the youngest girl s
Eldest boy is b+2
Eldest girl is s + 2

Total of ages is b+b+2+s+s+2 = 42
So 2b+2s=38

Youngest boy is double eldest girl
So b = 2(s+2) = 2s+4
So 2b = 4s+8

Substitute into total age equation
4s + 8 + 2s = 38
So 6s = 30
So s=5

The others are all older than the youngest girl so that's your answer

[janek]

Trial and error. About 5 mins, but was doing other stuff at he time...

[mumsneedwine]

Youngest is 7. Girls are 7 & 9 and boys are 14 & 12. Took me about 3 minutes and worked it out as knew they must all around 10 (42 /4) and then used a bit of trial and error.

[noblegiraffe]

Took me a couple of minutes but I'm a maths teacher

[mumsneedwine]

And I think I read it wrong (how many times do I tell the kids to read the question!). I'll try again !!

[mumsneedwine]

It's 5 !! So girls are 7 & 5 and boys are 16 & 14 (so youngest boy is double oldest girl). Quite enjoyed making brain work while cooking tea !

[notnagging]

I don't know how a 9 year old could find this fun.

[notnagging]

How long did it take you mumsneedswine?I've told him the answer so he's busy writing me another one

[amothersplaceisinthewrong]

Oh, my son used to love all this sort of thing. Ended up with a Maths degree

Took me about 5 mins, worked out like the first poster

[mumsneedwine]

Well once I'd read the question properly, it took a few minutes - but I do have a science degree and used to be a finance manager. Bit geeky and still love a bit of maths.

[Niceweather]

Not even going to attempt!

[CURIOUSMIND]

30 seconds!
youngest girl x, the oldest girl x+2, the youngest boy 2x+4, the oldest boy 2x+6.
x+(x+2)+(2x+4)+(2x+6)=42
x=5

[notnagging]

He wants to be an accountant. My family is proof that intelligence is not inherited. 30 seconds. I won't be saying how long it took me!

[noblegiraffe]

Go to YouTube and look up Dara O'Brian's School of Hard Sums. There are some nice puzzles on there, my secondary kids love the Chilli Chocolate game which is the second puzzle on episode 3. If you can understand the explanation of how to always win if you go first, you could beat him a few times and show him mum isn't that daft

[notnagging]

Thank you noblegiraffe. Will do

[TuftyFinch]

16, 14, 7 and 5.

[TuftyFinch]

Sorry I had to post that before it fell out of my head. It took about 4minutes in my head. I started at 12 for the youngest boy and was out by 2 just had to adjust by 2. I really enjoyed it but it hurt my head. I wanted to get a pen but struggled without. I'm quite pleased.
I don't know how to do it properly though.

[notnagging]

I was like that tufty. Once I cracked it just had to get it out but took me a lot longer

[TuftyFinch]

I keep looking at noblegiraffe and curiousmind's workings out but it's hurting my head! I do like maths problems but can't do them 'properly'. DCs are still little but (4 and 5) but I feel I need to steel myself for all if this to come

[notnagging]

I know what you mean tufty. I can't help mine with hwk

[Niceweather]

Thanks for link Noblegiraffe. My son loves Dara so I will sit him in front of it.