Are 45 and 28 coprime (prime to each other, relatively prime)?
45 and 28 are coprime (relatively prime) - if there is no number other than 1 that evenly divides the both numbers (without a remainder) - that is - if their greatest (highest) common factor (divisor), gcf (hcf, gcd), is 1.
Calculate the greatest (highest) common factor (divisor), gcf (hcf, gcd), of the numbers
Method 1. The prime factorization:
The prime factorization of a number: finding the prime numbers that multiply together to make that number.
45 = 32 × 5
45 is not a prime number, is a composite one.
28 = 22 × 7
28 is not a prime number, is a composite one.
The numbers that are only divisible by 1 and themselves are called prime numbers. A prime number has only two factors: 1 and itself.
A composite number is a natural number that has at least one other factor than 1 and itself.
Calculate the greatest (highest) common factor (divisor), gcf (hcf, gcd):
Multiply all the common prime factors of the two numbers, taken by their smallest exponents (powers).
But the numbers have no common prime factors.
gcf (hcf, gcd) (45; 28) = 1
Coprime numbers (prime to each other, relatively prime)
Coprime numbers (prime to each other, relatively prime) (45; 28)? Yes.
The numbers have no common prime factors.
gcf (hcf, gcd) (28; 45) = 1
Method 2. The Euclidean Algorithm:
This algorithm involves the process of dividing numbers and calculating the remainders.
'a' and 'b' are the two natural numbers, 'a' >= 'b'.
Divide 'a' by 'b' and get the remainder of the operation, 'r'.
If 'r' = 0, STOP. 'b' = the gcf (hcf, gcd) of 'a' and 'b'.
Else: Replace ('a' by 'b') and ('b' by 'r'). Return to the step above.
Step 1. Divide the larger number by the smaller one:
45 ÷ 28 = 1 + 17
Step 2. Divide the smaller number by the above operation's remainder:
28 ÷ 17 = 1 + 11
Step 3. Divide the remainder of the step 1 by the remainder of the step 2:
17 ÷ 11 = 1 + 6
Step 4. Divide the remainder of the step 2 by the remainder of the step 3:
11 ÷ 6 = 1 + 5
Step 5. Divide the remainder of the step 3 by the remainder of the step 4:
6 ÷ 5 = 1 + 1
Step 6. Divide the remainder of the step 4 by the remainder of the step 5:
5 ÷ 1 = 5 + 0
At this step, the remainder is zero, so we stop:
1 is the number we were looking for - the last non-zero remainder.
This is the greatest (highest) common factor (divisor).
gcf (hcf, gcd) (45; 28) = 1
Coprime numbers (prime to each other, relatively prime) (45; 28)? Yes.
gcf (hcf, gcd) (28; 45) = 1
The final answer:
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45 and 28 are coprime (relatively prime) - if there is no number other than 1 that evenly divides the both numbers (without a remainder) - that is - if their greatest (highest) common factor (divisor), gcf (hcf, gcd), is 1.
Coprime numbers (prime to each other, relatively prime) (45; 28)? Yes.
gcf (hcf, gcd) (45; 28) = 1
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