There are 15 boys and 10 girls in Miss Li's class.  She wants to group all the students so that each group has the same number of boys and the same number of girls. What is the greatest number of groups she can have? 

• 3 groups
• 2 groups
• 10 groups
• 5 groups

A pet shop manager wants the same number of birds in each cage.  He wants to use as few cages as possible, but can only have one type of bird in each cage.  If he has 42 parakeets and 18 canaries, how many birds will he put in each cage? 

• 3 birds per cage
• 2 birds per cage
• 6 birds per cage
• 18 birds per cage

What is the greatest common factor of 18 and 45?

• 5
• 2
• 9
• 1

What is the greatest common factor of 33 and 66?

• 11
• 3
• 33
• 22

What is the greatest common factor of 72 and 96?

• 2
• 24
• 12
• 48

What is the greatest common factor of 50 and 60?

• 5
• 10
• 15
• 30