Question
Download Solution PDFIn which of the pairs of the following numbers is none of the two numbers a prime number, but the two numbers are co-primes?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFFormula used:
Two numbers are co-primes if their greatest common divisor (GCD) is 1.
Calculation:
1) Pair (21, 35)
21 = 3 × 7
35 = 5 × 7
GCD(21, 35) = 7
Both numbers are not co-primes.
2) Pair (19, 27)
19 is a prime number.
Incorrect.
3) Pair (11, 17)
Both 11 and 17 are prime numbers.
Incorrect.
4) Pair (8, 25)
8 = 23
25 = 52
GCD(8, 25) = 1
Both 8 and 25 are not prime numbers.
Both numbers are co-primes.
∴ The correct answer is option 4.
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