Prime factors, common factors and common multiples
Answers are for parents and teachers.
1
Write 72 as a product of prime factors.
72 = 8 × 9 = 2 × 2 × 2 × 3 × 3.
2
Find the GCF and the LCM of 8 and 12.
GCF = 4 (common factors 1, 2, 4). LCM = 24 (multiples of 12: 12, 24; 24 ÷ 8 = 3).
3
List the prime numbers between 30 and 50.
31, 37, 41, 43, 47.
4
Marwan packs 36 pencils and 54 notebooks into identical gift bags with nothing left over. What is the greatest number of bags? What is in each?
GCF of 36 and 54 is 18, so 18 bags, each with 36 ÷ 18 = 2 pencils and 54 ÷ 18 = 3 notebooks.
5
Youssef visits his grandmother every 10 days and Nour every 12 days. They both visit today. After how many days do they visit on the same day again?
LCM of 10 and 12: multiples of 12 are 12, 24, 36, 48, 60, and 60 = 10 × 6. After 60 days.