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## Pre-algebra

### Course: Pre-algebra > Unit 1

Lesson 1: Factors and multiples# Reasoning about factors and multiples

CCSS.Math:

Use the equation 3x5=15 to understand the relationship between factors and multiples. Created by Sal Khan.

## Want to join the conversation?

- um... whats a factor of 78 plz help im cofuzed🤔(9 votes)
- The factors of 78 are 1,2,3,6,13,26,39,78.

To figure these out be sure to check the previous lesson on divisibility checks.(8 votes)

- ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣤⣤⣤⣶⣤⣤⣀⣀⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⣴⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣶⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣾⣿⣿⣿⣿⣿⡿⠋⠉⠛⠛⠛⠿⣿⠿⠿⢿⣇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣾⣿⣿⣿⣿⣿⠟⠀⠀⠀⠀⠀⡀⢀⣽⣷⣆⡀⠙⣧⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢰⣿⣿⣿⣿⣿⣷⠶⠋⠀⠀⣠⣤⣤⣉⣉⣿⠙⣿⠀⢸⡆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⣿⣿⣿⣿⣿⠁⠀⠀⠴⡟⣻⣿⣿⣿⣿⣿⣶⣿⣦⡀⣇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢨⠟⡿⠻⣿⠃⠀⠀⠀⠻⢿⣿⣿⣿⣿⣿⠏⢹⣿⣿⣿⢿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣼⣷⡶⣿⣄⠀⠀⠀⠀⠀⢉⣿⣿⣿⡿⠀⠸⣿⣿⡿⣷⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢻⡿⣦⢀⣿⣿⣄⡀⣀⣰⠾⠛⣻⣿⣿⣟⣲⡀⢸⡿⡟⠹⡆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢰⠞⣾⣿⡛⣿⣿⣿⣿⣰⣾⣿⣿⣿⣿⣿⣿⣿⣿⡇⢰⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⠀⣿⡽⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢿⠿⣍⣿⣧⡏⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣷⣿⣿⣿⣿⣿⣿⣿⣿⣷⣮⣽⣿⣷⣙⣿⡟⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡟⣹⡿⠇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠛⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡧⣦⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⡆⠀⠀⠀⠀⠀⠀⠀⠉⠻⣿⣿⣾⣿⣿⣿⣿⣿⣿⡶⠏⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⣀⣠⣤⡴⠞⠛⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠚⣿⣿⣿⠿⣿⣿⠿⠟⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⢀⣠⣤⠶⠚⠉⠉⠀⢀⡴⠂⠀⠀⠀⠀⠀⠀⠀⠀⢠⠀⠀⢀⣿⣿⠁⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠞⠋⠁⠀⠀⠀⠀⣠⣴⡿⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⣾⠀⠀⣾⣿⠋⠀⢠⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⡀⠀⠀⢀⣷⣶⣿⣿⣿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣆⣼⣿⠁⢠⠃⠈⠓⠦⣄⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⣿⣿⡛⠛⠿⠿⠿⠿⠿⢷⣦⣤⣤⣤⣦⣄⣀⣀⠀⢀⣿⣿⠻⣿⣰⠻⠀⠸⣧⡀⠀⠉⠳⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠛⢿⣿⣆⠀⠀⠀⠀⠀⠀⠀⠀⠈⠉⠉⠙⠛⠿⣦⣼⡏⢻⣿⣿⠇⠀⠁⠀⠻⣿⠙⣶⣄⠈⠳⣄⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠈⠋⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠁⣐⠀⠀⠀⠈⠳⡘⣿⡟⣀⡠⠿⠶⠒⠟⠓⠀⠹⡄⢴⣬⣍⣑⠢⢤⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⢀⣀⠐⠲⠤⠁⢘⣠⣿⣷⣦⠀⠀⠀⠀⠀⠀⠙⢿⣿⣏⠉⠉⠂⠉⠉⠓⠒⠦⣄⡀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠀⠀⠀⠀⠈⣿⣿⣷⣯⠀⠀⠀⠀⠀⠀⠀⠀⠉⠻⢦⣷⡀⠀⠀⠀⠀⠀⠀⠉⠲⣄⠀

⠠⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⢦⠀⢹⣿⣏⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⢻⣷⣄⠀⠀⠀⠀⠀⠀⠈⠳

⠀⠀⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠁⣸⣿⣿⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⣽⡟⢶⣄⠀⠀⠀⠀⠀

⠯⠀⠀⠀⠒⠀⠀⠀⠀⠀⠐⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢻⣿⣿⣷⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⣿⡄⠈⠳⠀⠀⠀⠀

⠀⠀⢀⣀⣀⡀⣼⣤⡟⣬⣿⣷⣤⣀⣄⣀⡀⠀⠀⠀⠀⠀⠀⠈⣿⣿⡄⣉⡀⠀⠀⠀⠀⠀⠀⠀⢀⠀⠀⠀⠀⠀⣿⣿⣄⠀⣀⣀⡀(8 votes) - how do i do fector pair?(5 votes)
- ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣤⣤⣤⣶⣤⣤⣀⣀⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⣴⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣶⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣾⣿⣿⣿⣿⣿⡿⠋⠉⠛⠛⠛⠿⣿⠿⠿⢿⣇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣾⣿⣿⣿⣿⣿⠟⠀⠀⠀⠀⠀⡀⢀⣽⣷⣆⡀⠙⣧⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢰⣿⣿⣿⣿⣿⣷⠶⠋⠀⠀⣠⣤⣤⣉⣉⣿⠙⣿⠀⢸⡆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⣿⣿⣿⣿⣿⠁⠀⠀⠴⡟⣻⣿⣿⣿⣿⣿⣶⣿⣦⡀⣇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢨⠟⡿⠻⣿⠃⠀⠀⠀⠻⢿⣿⣿⣿⣿⣿⠏⢹⣿⣿⣿⢿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣼⣷⡶⣿⣄⠀⠀⠀⠀⠀⢉⣿⣿⣿⡿⠀⠸⣿⣿⡿⣷⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢻⡿⣦⢀⣿⣿⣄⡀⣀⣰⠾⠛⣻⣿⣿⣟⣲⡀⢸⡿⡟⠹⡆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢰⠞⣾⣿⡛⣿⣿⣿⣿⣰⣾⣿⣿⣿⣿⣿⣿⣿⣿⡇⢰⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⠀⣿⡽⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢿⠿⣍⣿⣧⡏⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣷⣿⣿⣿⣿⣿⣿⣿⣿⣷⣮⣽⣿⣷⣙⣿⡟⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡟⣹⡿⠇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠛⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡧⣦⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⡆⠀⠀⠀⠀⠀⠀⠀⠉⠻⣿⣿⣾⣿⣿⣿⣿⣿⣿⡶⠏⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⣀⣠⣤⡴⠞⠛⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠚⣿⣿⣿⠿⣿⣿⠿⠟⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⢀⣠⣤⠶⠚⠉⠉⠀⢀⡴⠂⠀⠀⠀⠀⠀⠀⠀⠀⢠⠀⠀⢀⣿⣿⠁⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠞⠋⠁⠀⠀⠀⠀⣠⣴⡿⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⣾⠀⠀⣾⣿⠋⠀⢠⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⡀⠀⠀⢀⣷⣶⣿⣿⣿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣆⣼⣿⠁⢠⠃⠈⠓⠦⣄⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⣿⣿⡛⠛⠿⠿⠿⠿⠿⢷⣦⣤⣤⣤⣦⣄⣀⣀⠀⢀⣿⣿⠻⣿⣰⠻⠀⠸⣧⡀⠀⠉⠳⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠛⢿⣿⣆⠀⠀⠀⠀⠀⠀⠀⠀⠈⠉⠉⠙⠛⠿⣦⣼⡏⢻⣿⣿⠇⠀⠁⠀⠻⣿⠙⣶⣄⠈⠳⣄⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠈⠋⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠁⣐⠀⠀⠀⠈⠳⡘⣿⡟⣀⡠⠿⠶⠒⠟⠓⠀⠹⡄⢴⣬⣍⣑⠢⢤⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⢀⣀⠐⠲⠤⠁⢘⣠⣿⣷⣦⠀⠀⠀⠀⠀⠀⠙⢿⣿⣏⠉⠉⠂⠉⠉⠓⠒⠦⣄⡀⠀⠀⠀

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠀⠀⠀⠀⠈⣿⣿⣷⣯⠀⠀⠀⠀⠀⠀⠀⠀⠉⠻⢦⣷⡀⠀⠀⠀⠀⠀⠀⠉⠲⣄⠀

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⠀⠀⢀⣀⣀⡀⣼⣤⡟⣬⣿⣷⣤⣀⣄⣀⡀⠀⠀⠀⠀⠀⠀⠈⣿⣿⡄⣉⡀⠀⠀⠀⠀⠀⠀⠀⢀⠀⠀⠀⠀⠀⣿⣿⣄⠀⣀⣀⡀(4 votes) - This really helped me with factors! :] :) :-)(2 votes)
- what is 3 multiple 15(2 votes)
- well if you take 15 and multiply by 3 you will get 45(1 vote)

- 0/7 questions right i am a noob at this i never get a 100% (this is hard and don´t read this)(1 vote)
- Most math is like that at the start. Just keep practicing and you will master it completely! :)(3 votes)

- yo yo! your man is in da house!(1 vote)

## Video transcript

- [Instructor] We're told we know that five times three is equal to 15. Yep, that's true. So which of the following
statements are also true? And it says to choose two answers. So pause this video and see
if you can work through that. All right, now let's go
through them one by one. So this first one says,
"Three is a multiple of 15." Now, in order for three to be
able to be a multiple of 15, that means that we can multiply 15 by some whole number to get to three. But a multiple of 15,
we're thinking 15, 30, 45, it's not gonna be three. What whole number can I
multiple 15 by to get three? If I multiply 15 by
one, I'm already at 15. So this is not going to be our choice. And since it say pick two answers, well, we might be able to figure out it's these. But let's just read them to make sure that they make sense. 15 is a multiple of three. So that means I can multiply
three times some whole number to get to 15, and we know
what that whole number is. It's five. They tell us right over there. Five times three is 15. So 15 is a multiple of three. 15 would also be a multiple
of five 'cause I can multiply five by the whole
number three to get to 15. So I like this choice. Five is a factor of 15. Well, a factor, factors of a number are numbers that you can multiply together to get that number. So five is a factor of 15,
and three is a factor of 15, because five times three is 15. So this one is also true. It would've also been true if they'd said three is a factor of 15, or if they'd said 15
is a multiple of five. Any of those would have
been true statements based on what we know, that
five times three is equal to 15.