Lesson 17: Common Multiples | Unit 7: Rational Numbers

Multiple Choice

A green light blinks every 4 seconds, and a yellow light blinks every 5 seconds. When will both lights blink at the same time?

• Every 9 seconds

• Every 10 seconds

• Every 20 seconds

• Every 25 seconds

Multiple Choice

A red light blinks every 12 seconds, and a blue light blinks every 9 seconds. When will both lights blink at the same time?

• Every 36 seconds

• Every 21 seconds

• Every 18 seconds

• Every 24 seconds

Open Ended

Example 1: A green light blinks every 4 seconds, and a yellow light blinks every 5 seconds.

1. Example 2: A red light blinks every 12 seconds, and a blue light blinks every 9 seconds.

Explain how to tell when 2 lights blink together.

Multiple Choice

Which of the following lists all multiples of 10 up to 100?

• [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
• [20, 40, 60, 80, 100]
• [10, 30, 50, 70, 90]
• [5, 15, 25, 35, 45, 55, 65, 75, 85, 95]

Multiple Choice

Which of the following lists all multiples of 15 up to 100?

• [15, 25, 35, 45, 55, 65]
• [15, 30, 45, 60, 75, 90]
• [5, 10, 15, 20, 25, 30]
• [10, 20, 30, 40, 50, 60]

Multiple Choice

What is the least common multiple of 10 and 15?

• 25
• 35
• 30
• 20

Multiple Choice

Cups are sold in packages of 8. Napkins are sold in packages of 12. What is the fewest number of packages of cups and the fewest number of packages of napkins that can be purchased so there will be the same number of cups as napkins?

• 4 packages of cups and 1 package of napkins
• 1 package of cups and 5 packages of napkins
• 3 packages of cups and 2 packages of napkins
• 2 packages of cups and 3 packages of napkins

Multiple Choice

Cups are sold in packages of 8. Napkins are sold in packages of 12. How many sets of cups and napkins will there be if you buy 24 cups and 36 napkins?

• 3
• 5
• 4
• 2