Question 10306: While at the park, I saw boys and dogs. Counting heads, I got 32. Counting legs, I got 104. How many boys and dogs were there? Answer by Earlsdon(6294) (Show Source):
You can put this solution on YOUR website! Let B = number of boys and D = number of dogs.
And, of course, dogs have 4 legs (usually) and boys have 2 legs (normally) and boy and dogs each have 1 head (hopefully).
So, you can write:
Total number of legs. Total number of heads. Rewrite as: and substitute into the 1st equation.
Simplify and solve for D, the number of dogs.
Subtract 64 from both sides.
Divide both sides by 2.
There were 20 dogs.
There were 12 boys.
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