There are 13 animals in the barn. Some are chickens and some are pigs. There are 40 legs in all. How many of each animal are there?

Question

Please help I really don't understand some parts of the equation because they are confusing my teacher doesn't explain it well. Also I have another way to do it but my teacher doesn't like it a lot 

Answer 1

c + p = 13

2c + 4p = 40

 

We can do this a few ways, but let's solve the first for c and substitute.

 

c = 13 - p

 

Now, since c and 13 - p are equal, we can substitute one for the other.

 

2(13 - p) + 4p = 40

26 - 2p + 4p = 40

2p = 14

p = 7

 

c = 13 - 7 = 6

 

There are 7 pigs and 6 chickens.