Question

There are 21 animals in a zoo. Some are elephants and some are birds. There are 66 legs in all. How many elephants are in the zoo?

• A. $12$
• B. $13$
• C. $14$
• D. $15$

Answer 1

Answer: (A)

$12$

Let the number of elephants $=x$
Number of birds $=y$
Now form an equation as,
$x+y=21$ ----- (1)
There are 4 legs for elephant and 2 legs for bird.
So, the second equation becomes,
$4x+2y=66$ ----- (2)
From equation (1)
$y=21-x$
Put the value of $y$ in equation (2)
$4x+2(21-x)=66$
$4x+42-2x=66$
$2x=66-42$
$2x=24$
$x=\frac{24}{2}$
$x=12$
Therefore, there are 12 elephants in a zoo.