Another batch of 21 girls and 36 boys joined in, with an equal number of boys and girls in each group, what is the common number of members that can be formed?

3

• To find the common number of members that can be formed, find their GCF
• The factors of 21 are: 1, 3, 7, 21  
• The factors of 36 are: 1, 2, 3, 4, 6, 9, 12, 18, 36
• Therefore, the answer is 3.