Homework
- Kwacky
- Posts: 38733
- Joined: 21 Oct 2013, 21:52
- Your Bike: Brutale 800RR, 1000SX Ninja
- Location: Brum
- Has thanked: 4338 times
- Been thanked: 8391 times
Homework
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
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
- Posts: 15513
- Joined: 22 Oct 2013, 07:34
- Your Bike: Ducati 748/853 & Triumph Street Triple 765RS
- Location: Staffordshire
- Has thanked: 4187 times
- Been thanked: 4133 times
Re: Homework
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.
Are you certain the first equation is correct? The way it's written it could also be that Santa -80 = 3 x elf.
- Kwacky
- Posts: 38733
- Joined: 21 Oct 2013, 21:52
- Your Bike: Brutale 800RR, 1000SX Ninja
- Location: Brum
- Has thanked: 4338 times
- Been thanked: 8391 times
Re: Homework
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.
I do know the answer but had forgotten how to get there.
-
- Posts: 1387
- Joined: 07 Apr 2014, 16:38
- Your Bike: Daytona 675R
- Has thanked: 271 times
- Been thanked: 388 times
Re: Homework
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!
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!
Last edited by DaytonAndy on 03 Jan 2015, 02:56, edited 1 time in total.
-
- Posts: 1387
- Joined: 07 Apr 2014, 16:38
- Your Bike: Daytona 675R
- Has thanked: 271 times
- Been thanked: 388 times
Re: Homework
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
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
-
- Posts: 458
- Joined: 14 Mar 2014, 13:44
- Your Bike: '04 Triumph Daytona
- Has thanked: 68 times
- Been thanked: 94 times
Re: Homework
FWIW, Khan Academy online and YouTube has helped me with my daughters maths.
"When in doubt use full throttle. It may not improve the situation but it will end the suspense ".
- Jack
- Posts: 2629
- Joined: 11 Mar 2014, 21:49
- Your Bike:
- Has thanked: 1396 times
- Been thanked: 1636 times
- Contact:
Re: Homework
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 ????
ps - I got 7 ????
- D6Nutz
- Posts: 7475
- Joined: 21 Oct 2013, 21:26
- Your Bike: Speed Triple 1200 RS
- Has thanked: 828 times
- Been thanked: 2627 times
- Contact:
Re: Homework
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.
You never really learn to swear until you learn to drive.
If everything seems under control, you're not going fast enough - Mario Andretti
If everything seems under control, you're not going fast enough - Mario Andretti
- Blade
- Posts: 18772
- Joined: 14 Mar 2014, 18:43
- Your Bike: Kawasaki ZX10R
- Location: North West
- Has thanked: 3134 times
- Been thanked: 3767 times
Re: Homework
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
Well explained Andy its easy when you break it down as you have
- R34PER
- Posts: 319
- Joined: 12 Mar 2014, 09:35
- Your Bike: Yamaha XJ6-N
- Has thanked: 85 times
- Been thanked: 42 times
Re: Homework
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
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
- Posts: 13021
- Joined: 22 Sep 2014, 11:36
- Your Bike: Triumph Daytona 650.
- Has thanked: 4310 times
- Been thanked: 1137 times
Re: Homework
This sorta thing is exactly why I don't believe in Santa.....no train set is worth all that!