# Week 1 Review Answers and Solutions

Below are the solutions and answers to the Practice** Exercises and Problems for the Week 1** Review on LCM and GCD.

**Practice Exercises**

I. Find the GCD of each of the following.

a.) 6, 10

Answer: 2

b.) 18, 42

Answer: 6

c.) 12, 48, 60

Answer: 12

d.) 56, 72

Answer: 8

e.) 225, 75

Answer: 75

II. Find the LCM of each of the following.

a.) 3, 4

Answer: 12

b.) 2, 5

Answer: 10

c.) 3, 6, 8

Answer: 24

d.) 3, 4, 5

Answer: 60

e.) 6, 12, 15

Answer: 60

**III. Practice Problems Solutions and Answers**

1.) 24 (GCD of 3, 4, and 8)

2.) 15 (GCD of 3 and 15)

3.) Solution: GCD of 3, 7, and 21 is 42. They will be seen in the gym on the same day in 42 days. Since June has 30 days, we need an additional 12 days to complete the 42 days. Therefore, they will be seen on the same day on July 12 (of the same year of course).

Answer: July 12

4.) Solution: The LCM of the two sequences is 12 and since we are looking for the tenth common number, we multiply 12 by 10. This gives us 120.

Answer: 120

5.) (a) Solution: LCM of 24 and 30 is 6. That is 6 groups.

(b) Solution: From (a) we can form 6 groups. There are 30 + 24 = 54 students. So in each group, there are 54/6 = 9 members. Since there are 6 groups, we divide each Grade level by 6. That is, 24/6 = 6 Grade 11 and 30/6 = 5 Grade 12 students in each group.

Answer: 4 Grade 11 students and 5 Grade 12 students.

6.) Reduce 42/56 to lowest terms.

Solution: GCD of 42 and 56 is 14. 42 divided by 14 is 3 and 56 divided by 14 is 4. Therefore, the lowest terms is 3/4.

Answer: 3/4

7.) Answer: 24 (LCM of 6 and 8)

8.) Answer: 6 (GCD of 18 and 12)

9.) Solution: The GCD of 21, 35, and 84 is 7. So, the cube has a side length of 7 cm.

Answer: 7 by 7 by 7

10.) Answer: 30 (GCD of 3, 5, and 6).