Answer:
9. 60
10. 12
Explanation:
9.
We need to find the least common multiple (LCM) of 12 and 15.
Here are two methods:
Method 1
List several multiples of each number until you find the smallest number that is a multiple of both.
Multiples of 12: 12, 24, 36, 48, 60, 72
Multiples of 15: 15, 30, 45, 60, 75
60 is the LCM of 12 and 15.
Answer: 60
Method 2
Find the prime factorization of both numbers.
12 = 2² × 3
15 = 3 × 5
The LCM is the product of the following factors:
Common and not common prime factors with greater exponent.
2 is not common. Use 2².
3 is common. Use 3.
5 is not common. Use 5.
LCM = 2² × 3 × 5 = 60
Answer: 60
10.
We need the LCM of 4 and 6.
I'll use the second method above which is prime factorization.
4 = 2²
6 = 2 × 3
LCM = 2² × 3 = 12
Answer: 12