Problem solving: Least common multiple

During a car race, two competitors will stop to fill up the fuel tank. One does it every 4 laps, and the other every 5 laps.

When the race begins, after how many laps will they meet at the fuel station, if they travel at the same speed?


Solution


The first competitor refill the tank every 4 laps


The first competitor will refill the tank after 4 laps, 8 laps, 12 laps, etc...


The situation is shown below

4, 8, 12, 16, 20, 24, 28, 32, 36

40, 44, 48, 52, 56, 60


The other competitor will refill the tank after 5 laps, 10 laps, 15 laps, etc...


The situation is shown below

5, 10, 15, 20, 25, 30, 35, 40

45, 50, 55, 60



The number in bold are what they have in common.


They will meet at the gas station after 20 laps, 40 laps, 60 laps, etc..

The least number they have in common is 20

We can also call this number the least common multiple.

Click here to post comments

Join in and write your own page! It's easy to do. How? Simply click here to return to Basic math word problem.

Recent Articles

  1. Fundamental Counting Principle

    Jun 06, 23 07:32 AM

    Multiplication principle and addition principle
    The fundamental counting principle is introduced in this lesson. Learn how to count with the multiplication principle and the addition principle.

    Read More

  2. 45-45-90 Triangle

    May 01, 23 07:00 AM

    45-45-90 triangle
    What is a 45-45-90 triangle? Definition, proof, area, and easy to follow real-world examples.

    Read More

Tough algebra word problems

100 Tough Algebra Word Problems.

If you can solve these problems with no help, you must be a genius!

Math quizzes

 Recommended

Math vocabulary quizzes