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If (a=2^r\times3^2) has (15) positive factors, what is the value of (r)?
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Answer and explanation
Correct answer: (4)
Step 1: Total factors are ((r+1)(2+1)). Step 2: ((r+1)\times3=15), so (r+1=5) and (r=4). Step 3: Write the factor-count formula first, then solve the simple equation.
Frequently asked questions
What is the correct answer to this question?
(4)
Why is this the correct answer?
Step 1: Total factors are ((r+1)(2+1)). Step 2: ((r+1)\times3=15), so (r+1=5) and (r=4). Step 3: Write the factor-count formula first, then solve the simple equation.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Real Numbers. Topic: Prime Factorisation.
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