Least Common Multiple Word Problems

Two neon signs are turned on at the same instant and begin to blink. One sign blinks every 9 seconds. The other blinks every 15 seconds. In how many seconds will they blink together?

• 3

• 5

• 45

• 9

The school cafeteria serves tacos every sixth school day and cheeseburgers every eighth school day. If tacos and cheeseburgers are both on today's menu, in how many school days will they both be on the menu again?

• 24

• 2

• 6

• 12

Two clocks are started at the same moment. One chimes every 15 minutes. The other chimes every 25 minutes. In how many minutes will they chime together?

• 5

• 75

• 15

• 25

A radio station is giving away a $100 bill to every 30th caller and movie tickets to every 40th caller.  Which caller will be the first to win both prizes?

• 5
• 2
• 10
• 120

Mitra and Malcolm are both building a toy train track out of connecting pieces. Melanie has pieces that are 8 inches long while Martin's pieces are 20 inches long. How long will the shortest track be that they can each build with the same length?

• 2

• 40

• 4

• 20

Colette and Lin are traveling around a circular track. Colette is using her wheelchair and takes 7 minutes to make one loop. Lin is walking and takes 12 minutes to make one loop. If they start at the same time, in how many minutes will they meet each other again?

• 1

• 7

• 84

• 12

Vanessa began filling in the multiples of 3 and 9 in the Venn diagram. What is the smallest number that can they can appropriately place in the middle of the diagram?

• 18

• 9

• 27

• 3

You and Mr. Baird are jogging around school property. It takes you 6 minutes and Mr. Baird 8 minutes to go around once. If you start at the same time in front of the school, how long until you meet him again at the front?

• 12

• 16

• 24

• 36

• 48

A red subway arrives at the station every 5 minutes. The blue subway comes every 8 minutes. If they are both at the station now, how long will it be until they are both at the station again?

• 20

• 24

• 35

• 40