Posted by **Anonymous** on Thursday, March 7, 2013 at 7:10am.

A farm rears 9 ducks and cows in his farm. There are 28 legs altogether.How many ducks are there in the farm?

- Maths -
**Dr. Jane**, Thursday, March 7, 2013 at 10:24am
d + c = 9

2d + 4c = 28

Multiply the top equation by -2 and add. This will give you the number of cows. Find the ducks by substituting into the first equation.

- Maths -
**nanayeboahford**, Thursday, March 7, 2013 at 1:33pm
let d=number of ducks reared

c=number of cows reared

sum of ducks and cows=d+c=9

sum of their legs=2d+4c=28 since duck has two legs and cow also has 4 legs

the two equations give

d+c=9...1

2d+4c=28...2

multiply eqn 1 by 2

2(d+c=9) which gives 4d+4c=18..3

now 2d+4c=28

-2d+2c=18

we have 2c=10

therefore c=5 put c into eqn..1

to get d+5=9

d=4 meaning there are 4 ducks and 5 cows.proof2*4=8legs in all does 4 ducks and 4*5=20 legs in all does 5 cows.

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