Homework

[Kwacky]

My daughter is asking me for help with her homework. I'm having to point out I've not done any of this stuff for about 30 years. I may as well do some revision.

Anyone any good at simultaneous equations? I thought I could do them but this one has me stumped.

Santa is 3 times the age of an elf, less 80
Twice Santa's age ad 3 times the elfs age is 605

3y - 80 = x
2x + 3y = 605

[duke63]

Transfer your x = 3y-80 into the second equation. That is your second equation now reads 2(3y-80)+3y=605.

Are you certain the first equation is correct? The way it's written it could also be that Santa -80 = 3 x elf.

[Kwacky]

That's the way I've set it out. The question says that Santa's age is 3 times that of the elf, less 80

I do know the answer but had forgotten how to get there.

[DaytonAndy]

Santa is 3 times the age of an elf, less 80
Twice Santa's age add 3 times the elfs age is 605

s=3e-80
2s+3e=605 therefore 2s=605-3e

Now double both sides of the first equation: 2s=6e-160
We now know 605-3e=6e-160 so...
765-3e=6e
765=9e
e=85 put that into the first equation s=3e-80
s=255-80
s=175

Disclaimer: It's late and I might be wrong!

[DaytonAndy]

Or without going round the houses:
s=3e-80 therefore 3e=s+80
2s+3e=605 therefore 3e=605-2s
Since 3e must equal 3e:
605-2s=s+80
605=3s+80
525=3s
175=s

[Mac]

FWIW, Khan Academy online and YouTube has helped me with my daughters maths.

[bb41]

In a word .....no

[Jack]

Santa is ageless - the guy messes with time in order to get all his deliveries done , therefore its a trick question .
ps - I got 7 ????

[D6Nutz]

I'm so glad my mum is a retired teacher. I know where the little nutz's will be going for help with their homework when it gets that complicated.

[Blade]

I always thought I would be able to my kids with homework now I know I can't and will need some revision myself.

Well explained Andy its easy when you break it down as you have

[R34PER]

I didn't look at anything else first but I get stuff like this wrong all the time, i'll try anyway. Edited to add that I got it wrong I subtracted the 160 where I should have added it when working out the 2 santas and the 3 elves but it was obvious from my original answer that there must have been a mistake.

Santa is 3 times the age of an elf, less 80

Twice Santa's age ad 3 times the elfs age is 605

(2 x santa + 160) + 3 x elves = 6 elves + 3 elves

605 + 160 = 9 elves = 765

765 / 9 elves = 1 elf = 85

1 santa = 3 elves - 80

1 santa = (85 x 3) - 80

1 santa = 255 - 80 = 175

santa = 175
elf = 85

I put the + and - of the 160 in the wrong place the first time

[D41]

This sorta thing is exactly why I don't believe in Santa.....no train set is worth all that!