LCM of 7 and 9
2026-02-28 12:40 Diff

335 Learners

Last updated on August 5, 2025

LCM is a common multiple, the smallest value between the numbers 7 and 9. Did you know? We apply LCM unknowingly in everyday situations like setting alarms and to synchronize traffic lights and when making music.

What is the LCM of 7 and 9?

LCM of 7 and 9 Using Listing the Multiples

Step 1: Write down the multiples of the numbers. Don’t stop too early.


Multiples of 7 = 7, 14,21,28,35,42,49,56,63,70,…


Multiples of 9 = 9,18,27,36,45,54,63,…


Step 2:Find the smallest number common between the written multiples of 3 and 8


The smallest common multiple is 63


Thus, LCM(7,9) = 63

LCM of 7 and 9 Using Prime Factorization

Step 1: factorize the numbers into its prime factors 


7 = 7×1


9 = 3×3


Step 2: find the highest powers of the factors of 7 and 9


Step 3: Multiply the highest powers 


LCM(7,9) = 63

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LCM of 7 and 9 Using Division Method

  • Write the numbers 7,9 in a row 
  • Divide them by their common prime factors, if there is one
  • Carry forward the numbers that are left undivided by the previously chosen factor
  • Continue dividing until the remainder is ‘1’ 
  • Multiply the divisors to find the LCM
  • LCM(7,9) = 63
     

Common Mistakes and how to avoid them while finding the LCM of 7 and 9

Listed here are a few mistakes that one can commit when trying to find the LCM of the numbers 7 and 9. Try to avoid them. 
 

Problem 1

The LCM of 7 and 9 is 63. If the LCM increases by 20%, what is the new value?

Okay, lets begin

Increase = 20%×63=0.2×63=12.6


New LCM = 63+12.6=75.6
 

Explanation

 A 20% increase in the LCM of 63 results in 75.6.
 

Well explained 👍

Problem 2

Simplify the fraction LCM(7,9)/GCF(7,9).

Okay, lets begin

LCM(7,9)=63, GCF(7,9)=1


Simplified fraction: 63/1=63
 

Explanation

The LCM divided by the GCF gives the value of the LCM in this case.
 

Well explained 👍

Problem 3

A car mechanic services a red car every 7 days and a blue car every 9 days. If the cars are serviced today, when will they be serviced next together?

Okay, lets begin

The LCM of 7 and 9 is 63. 
 

Explanation

Both cars will be serviced again in 63 days. The LCM of 7 and 9 is 63, which is the smallest common time interval for the given digits. 
 

Well explained 👍

FAQs on LCM of 7 and 9

1.What is the HCF of 7 and 9?

Factors of 7 are 1,7 


Factors of 9 are 1,3,9


7 and 9 share no common factors but 1, therefore, the HCF is 1. 
 

2.What are the multiples of 7 and 9?

Multiples of 7: 7,14,21,28,35,42,49,56,63,…


Multiples of 9: 9,18,27,36,45,54,63,…


The least common multiples of 7 and 9 = 63
 

3.What is the LCM of 7,9,21 and 1?

63 is the smallest number that appears commonly on the lists of the numbers 7,9,21 and 1. 


LCM (1,7,9,21)= 63
 

4.What is divisible by 7 and 9?

The LCM of 7,9 is 63, therefore, all multiples of 63 are divisible by 7 and 9. A few of these numbers include,

63,126,189,252,315,378,441 and so on. 
 

5.What is the LCM of 6,7,9 and 12?

252 is the smallest number that appears commonly on the lists of the numbers 6,7,9 and 12


LCM(6,7,9,12) = 252 
 

Important glossaries for the LCM of 7 and 9

  • Multiple — product of a number and a natural integer
  • Prime factor — number one gets after prime factorization any given number 
  • Prime factorization — the process of breaking the number into its prime factors. 
     

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Hiralee Lalitkumar Makwana

About the Author

Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.

Fun Fact

: She loves to read number jokes and games.