Question

1. there were four girls and six boys at a party. they took turns dancing with one another, but a girl never danced with a girl and a boy never danced with a boy. how many different couples could they form for dancing? a 20 b 10 c 9 d 24

Explanation:

Step1: Calculate total unrestricted couples

Each girl can pair with 6 boys, so total pairs: $4 \times 6 = 24$

Step2: Subtract invalid same-girl pairs

There are 4 invalid girl-girl pairs, so valid pairs: $24 - 4 = 20$

Answer:

A. 20