If G={x∈N: x is a common factor of 15 and 25}, what is G?
Answer and explanation
Correct answer: G={1,5}
A common factor must divide both numbers exactly. The positive factors of 15 are 1, 3, 5, and 15, while the positive factors of 25 are 1, 5, and 25. Their intersection is therefore {1,5}, so option A is correct. Although 3 and 15 divide 15, they do not divide 25, and 10 divides neither number. Hence they cannot belong to G.
Frequently asked questions
What is the correct answer to this question?
G={1,5}
Why is this the correct answer?
A common factor must divide both numbers exactly. The positive factors of 15 are 1, 3, 5, and 15, while the positive factors of 25 are 1, 5, and 25. Their intersection is therefore {1,5}, so option A is correct. Although 3 and 15 divide 15, they do not divide 25, and 10 divides neither number. Hence they cannot belong to G.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Number Systems.
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