• Jan 5th 2006, 10:29 AM
lacourse
ratios
my 11yr old has been given some homework on ratios that i'm finding hard,
A farm has some chickens & some rabbits.
Altogether there are:
94 legs
How many chickens are there?
and how many rabbits are there?
Any help would be great
• Jan 5th 2006, 11:10 AM
ticbol
Quote:

Originally Posted by lacourse
my 11yr old has been given some homework on ratios that i'm finding hard,
A farm has some chickens & some rabbits.
Altogether there are:
94 legs
How many chickens are there?
and how many rabbits are there?
Any help would be great

Chicken has two legs; rabbit has 4 legs.

Let c = number of chickens in there; and r = number of rabbits.

c*1 +r*1 = 35
c +r = 35 -------------(1)

Re legs:
c*2 +r*4 = 94
2c +4r = 94
Reduce that to its "lowest term", divide both sides by 2,
c +2r = 47 ------------(2)

One way to continue is by substitution.
From (1), c = 35-r
Substitute that into (2),
35-r +2r = 47
2r -r = 47 -35
r = 12
So, c = 35 -12 = 23

Therefore, there are 23 chickens and 12 rabbits in there. ------answer.

---------
Check.

c +r = 35
23 +12 =? 35
35 =? 35
Yes, so, OK.

Re legs,
2c +4r = 94
2*23 +4*12 =? 94
46 +48 =? 94
94 =? 94
Yes, so, OK.
• Jan 5th 2006, 11:15 AM
CaptainBlack
Quote:

Originally Posted by lacourse
my 11yr old has been given some homework on ratios that i'm finding hard,
A farm has some chickens & some rabbits.
Altogether there are:
94 legs
How many chickens are there?
and how many rabbits are there?
Any help would be great

As there are 35 heads we have 35 creatures altogether.
Counting two legs of each would account for a total of
70 legs, leaving 24 legs unaccounted for, which must
belong to 12 rabbits (to give each rabbit four legs)

So we have 12 rabbits and 23 chickens.

RonL
• Jan 5th 2006, 12:11 PM
lacourse
Thanks,
My daughter will be pleased :)