Question

each cow has 4 legs and each chicken has 2 legs. If a boy counts 42 heads and 144 feet, how many cows are there?

Answer 1

Solution:

we are given that

Each cow has 4 legs and each chicken has 2 legs.

A boy counts 42 heads and 144 feet.

we have been asked to find how many cows are there?

Let there are x cows and y chicken.

Then we can write

$x+y=42....(i)\\ \\ \text{Sum of Heads}\\ \\ 4x+2y=144\\ \\\\\text{Sum of feet }\\ \\ \Rightarrow 2x+y=72....(ii)\\ \\ \text{Now solve these two equation together we get}\\ \\\\2x+(42-x)=72\\ \\ 2x+42-x=72\\ \\ x=72-42=30$

Hence Number of cows=30