As the name implies, Euclid's division algorithm is involved with the divisibility of integers.

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Euclid's Division Algorithm

Euclid's division algorithm is a technique for calculating the HCF of two numbers using Euclid's division lemma.

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Euclid's Division Algorithm

According to Euclid’s Division Lemma ( or Theorem),  "Any positive integer 'a' can be divided by another positive integer 'b' in such a way that a remainder 'r' is less than 'b'."

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Euclid’s Division Lemma

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In other words, Euclid’s Division Lemma states that,   "For any given two positive integers 'a' and 'b', there exist unique integers 'q' and 'r' satisfying the condition: a = bq + r, where 0 ≤ r < b."

Euclid’s Division Lemma

Here, integer 'a' is the dividend, 'b' is the divisor, 'q' is the quotient and 'r' is the remainder, and 'q' or 'r' can also be zero.

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Euclid’s Division Lemma

So, the above condition: a = b q + r ; can be expressed mathematically as: Dividend = Divisor × Quotient + Remainder It is called the Formula of the Euclid Division Algorithm.

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Formula of the Euclid Division Algorithm

Example:  Consider the pair of integers: 29, 3. If we divide a=29 by b=3, then we get the quotient as q=9 and the remainder as r=2, as shown follows:

Similarly, we can write the following relations:  Dividend = Divisor × Quotient + Remainder;  for each such pair: (i) For the pair: 17, 6:      17 = 6 × 2 + 5 (ii) For the pair: 5, 15:       5 = 15 × 0 + 5 (iii) For the pair: 24, 4:        24 = 4 × 6 + 0

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Examples:

Apply the following steps to find the HCF of two positive integers, say a and b, with a > b using Euclid's division algorithm: --->

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Find HCF using Euclid's Division Algorithm:

Apply Euclid’s division lemma to a and b, to find whole numbers, q and r such that a = bq + r, where 0 ≤ r < b

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Step 1:

If r = 0, then the HCF of a and b is, bIf r ≠ 0, apply the Euclid’s division lemma to b and r.

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Step 2:

Repeat the process until the remainder is zero.  At this stage, the divisor will be the required HCF.

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Step 3:

This algorithm works because  HCF (a, b) = HCF (b, r). The symbol HCF (a, b) denotes the HCF of a and b, etc.

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Find HCF using Euclid's Division Algorithm:

Solution: Apply the steps below to find HCF --->

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Example:  Use Euclid’s algorithm to find the HCF of 24 and 36.

Step 1: Since 36 > 24, apply the division lemma to 36 and 24, to get     36 = 24 × 1 + 12 Step 2: Since the remainder 12 ≠ 0, again apply the division lemma to divisor 24 and remainder 12, to get     24 = 12 × 2 + 0 The remainder has now become zero, so stop this process. Since the divisor at this stage is 12, the HCF of 36 and 24 is 12.

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There are many applications of Euclid’s division lemma/algorithm related to finding properties of numbers. Here are some examples of these applications:

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Applications of Euclid’s division lemma/algorithm

1. Every positive even integer 'm' has the form '2n', where n is an integer. 2. Every positive odd integer 'm' has the form '2n+1', where n is an integer.

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Applications of Euclid’s division lemma/algorithm

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