What is the GCF and LCM of 21 and 28?

Example 2: Find the GCF of 21 and 28, if their LCM is 84. Therefore, the greatest common factor of 21 and 28 is 7. Example 3: For two numbers, GCF = 7 and LCM = 84. If one number is 28, find the other number.

What are the factors of 21 and 28?

For 21 and 28 those factors look like this:

• Factors for 21: 1, 3, 7, and 21.
• Factors for 28: 1, 2, 4, 7, 14, and 28.

What is ladder method?

What is the Ladder Method Anyway? It is a simple technique that uses prime numbers and visualization in the form of staggering lines (in a way that looks like a ladder) to help students understand math problems. It requires students to show their work, but helps them clearly see how to arrive at a given solution.

Whats the LCM of 28 and 21?

84
Answer: LCM of 21 and 28 is 84.

Whats the HCF of 21 and 28?

So the greatest common factor 21 and 28 is 7.

What is the LCM of 28?

The LCM of 28 and 42 is 84. To find the LCM (least common multiple) of 28 and 42, we need to find the multiples of 28 and 42 (multiples of 28 = 28, 56, 84, 112; multiples of 42 = 42, 84, 126, 168) and choose the smallest multiple that is exactly divisible by 28 and 42, i.e., 84.

What is the LCM of 21 21?

What is the LCM of 21 and 21? The LCM of 21 and 21 is 21.

What’s the LCM of 21 and 28?

How do you use the ladder method?

Using the ladder Method, think about the smallest prime number that will go into both 24 and 36. When your child answers “2”, ask them how many times 2 goes into both 24 and 36. You’ll write the answers in the separate rungs below the numbers.

What is the LCM of 21 and 28?

The LCM of 21 and 28 is 84. Steps to find LCM Find the prime factorization of 21 21 = 3 × 7

How do you use an LCM calculator with steps?

This LCM calculator with steps finds the LCM and shows the work using 5 different methods: Find the smallest number that is on all of the lists. We have it in bold above. Find all the prime factors of each given number. List all the prime numbers found, as many times as they occur most often for any one given number.

How does the ladder method help students find GCF and LCM?

In addition to helping math students find GCF and LCM, using the ladder method helps students see the relationships between numbers a little more clearly. It’s very easy to see what factors different numbers have in common and how those factors ‘contribute’ to the LCM or GCF.

What are the advantages of using the ladder method?

2) In addition to helping math students find GCF and LCM, using the ladder method helps students see the relationships between numbers more clearly. It’s very easy to see what factors the numbers have in common and how those factors ‘contribute’ to the LCM or GCF. Ladder Method for Factoring