Question

A man visited a pet shop, and found only cats and birds. He counted a total of 200 heads and 580 legs. How many birds are there in the pet shop?

• A. 100
• B. 110
• C. 120
• D. 130
• E. None of these

Answer 1

The correct option is B

110

By alligation rule: Rule of alligation is applicable to the number of legs per head.

$\text{Average number of legs per head}=\frac{580}{200}=\frac{29}{10}$

$\text{Cats:Birds}=9:11\text{Number of birds}=\frac{200}{9+11}\times 11=110$