Finding the GCD of Three Numbers

Oct 13, 2025 by talynt.org 106 views

Exercise 2.321: Finding the Greatest Possible Length of Equal Pieces

In this exercise, we are given three strings of different lengths: 78 cm, 117 cm, and 351 cm. Our goal is to cut these strings into equal lengths. To find the greatest possible length of each piece, we need to determine the greatest common divisor (GCD) of the three lengths. The GCD is the largest number that divides each of the given lengths without leaving a remainder.

Understanding the Greatest Common Divisor (GCD)

The GCD of two or more numbers is the largest number that divides each of the given numbers without leaving a remainder. For example, the GCD of 12 and 18 is 6, because 6 is the largest number that divides both 12 and 18 without leaving a remainder.

Finding the GCD of Three Numbers

To find the GCD of three numbers, we can use the following steps:

Find the GCD of two numbers using the Euclidean algorithm.
Find the GCD of the result from step 1 and the third number using the Euclidean algorithm.

Euclidean Algorithm

The Euclidean algorithm is a method for finding the GCD of two numbers. It works by repeatedly dividing the larger number by the smaller number and taking the remainder. The process is repeated until the remainder is zero. The last non-zero remainder is the GCD.

Applying the Euclidean Algorithm

Let's apply the Euclidean algorithm to find the GCD of 78 and 117.

Divide 117 by 78: 117 = 78 × 1 + 39
Divide 78 by 39: 78 = 39 × 2 + 0

The last non-zero remainder is 39, so the GCD of 78 and 117 is 39.

Finding the GCD of 39 and 351

Now, let's find the GCD of 39 and 351 using the Euclidean algorithm.

Divide 351 by 39: 351 = 39 × 9 + 0

The last non-zero remainder is 39, so the GCD of 39 and 351 is 39.

The greatest possible length of each piece is 39 cm. This is because 39 is the largest number that divides each of the given lengths without leaving a remainder.

Real-World Application

This problem has a real-world application in carpentry and woodworking. When cutting wood into equal lengths, it's essential to find the greatest possible length to minimize waste and ensure accurate cuts.

Example Use Case

Suppose we have three wooden planks of lengths 78 cm, 117 cm, and 351 cm. We want to cut them into equal lengths for a furniture project. Using the GCD, we can determine that the greatest possible length of each piece is 39 cm. We can then cut each plank into 39 cm pieces, ensuring accurate and efficient cuts.

Tips and Variations

To find the GCD of more than three numbers, we can use the same steps as above.
To find the GCD of a number and a list of numbers, we can use the same steps as above.
To find the GCD of a list of numbers, we can use the same steps as above.

In conclusion, finding the greatest possible length of equal pieces involves determining the greatest common divisor (GCD) of the given lengths. The GCD is the largest number that divides each of the given lengths without leaving a remainder. By using the Euclidean algorithm, we can find the GCD of two or more numbers. This problem has a real-world application in carpentry and woodworking, and it's essential to find the greatest possible length to minimize waste and ensure accurate cuts.
Exercise 2.321: Finding the Greatest Possible Length of Equal Pieces - Q&A

In our previous article, we discussed how to find the greatest possible length of equal pieces by determining the greatest common divisor (GCD) of the given lengths. In this article, we will answer some frequently asked questions related to this topic.

Q: What is the greatest common divisor (GCD)?

A: The greatest common divisor (GCD) is the largest number that divides each of the given lengths without leaving a remainder.

Q: How do I find the GCD of two numbers?

A: You can use the Euclidean algorithm to find the GCD of two numbers. The Euclidean algorithm works by repeatedly dividing the larger number by the smaller number and taking the remainder. The process is repeated until the remainder is zero. The last non-zero remainder is the GCD.

Q: How do I find the GCD of three numbers?

A: To find the GCD of three numbers, you can use the following steps:

Find the GCD of two numbers using the Euclidean algorithm.
Find the GCD of the result from step 1 and the third number using the Euclidean algorithm.

Q: What is the Euclidean algorithm?

A: The Euclidean algorithm is a method for finding the GCD of two numbers. It works by repeatedly dividing the larger number by the smaller number and taking the remainder. The process is repeated until the remainder is zero. The last non-zero remainder is the GCD.

Q: How do I apply the Euclidean algorithm?

A: Let's apply the Euclidean algorithm to find the GCD of 78 and 117.

Divide 117 by 78: 117 = 78 × 1 + 39
Divide 78 by 39: 78 = 39 × 2 + 0

The last non-zero remainder is 39, so the GCD of 78 and 117 is 39.

Q: What is the greatest possible length of equal pieces?

A: The greatest possible length of equal pieces is the GCD of the given lengths. In this case, the greatest possible length of equal pieces is 39 cm.

Q: How do I use the GCD in real-world applications?

A: The GCD has many real-world applications, including carpentry and woodworking. When cutting wood into equal lengths, it's essential to find the GCD to minimize waste and ensure accurate cuts.

Q: What are some tips and variations for finding the GCD?

A: Here are some tips and variations for finding the GCD:

To find the GCD of more than three numbers, you can use the same steps as above.
To find the GCD of a number and a list of numbers, you can use the same steps as above.
To find the GCD of a list of numbers, you can use the same steps as above.

In conclusion, finding the greatest possible length of equal pieces involves determining the greatest common divisor (GCD) of the given lengths. The GCD is the largest number that divides each of the given lengths without leaving a remainder. By using the Euclidean algorithm, we can find the GCD of two or more numbers. This problem has many real-world applications, and it's essential to find the GCD to minimize waste and ensure accurate cuts.

Q: What is the greatest common divisor (GCD)?
A: The greatest common divisor (GCD) is the largest number that divides each of the given lengths without leaving a remainder.
Q: How do I find the GCD of two numbers?
A: You can use the Euclidean algorithm to find the GCD of two numbers.
Q: How do I find the GCD of three numbers?
A: To find the GCD of three numbers, you can use the following steps:
1. Find the GCD of two numbers using the Euclidean algorithm.
2. Find the GCD of the result from step 1 and the third number using the Euclidean algorithm.

GCD: Greatest common divisor
Euclidean algorithm: A method for finding the GCD of two numbers
Remainder: The amount left over after dividing one number by another

[1] "Greatest Common Divisor" by Math Open Reference
[2] "Euclidean Algorithm" by Khan Academy