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Director
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What is the easy way to find all the factors that are [#permalink]
 17 Mar 2004, 10:18
What is the easy way to find all the factors that are between 6 and 120, both inclusive, for 240?
One way is to write all the factors and pick only those that statisfy this
condition. Is there any other better way?
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Senior Manager
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Well, I can only think about one other method although I'm not sure if it's necessarily faster.
240 = 2^4*3*5
2*3 = 6
2^3*3*5 = 120
So you can try different combo's of anything between 2*3 and 2^3*3*5. So I guess you can use the combinations formula to figure that out but this sounds like a longer method.
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Manager
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240 = 2^4*3*5
# of factors for 240 = 5*2*2 = 20
Less factors that are not between 6 nd 120: 1, 2, 3, 4, 5 and 240 = 6
Factors between= 20-6 = 14
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Senior Manager
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Mantha,
You said: "# of factors for 240 = 5*2*2 = 20 "
How did you get 5, 2 and 2? Did you add 1 to each raised exponent?
I.E. 4 + 1 = 5
0 + 1 = 1
0 + 1 = 1
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Manager
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You said: "# of factors for 240 = 5*2*2 = 20 "
How did you get 5, 2 and 2? Did you add 1 to each raised exponent?
I.E. 4 + 1 = 5
1+1 = 2 not 0 + 1 = 1
1+1 = 2 not 0 + 1 = 1
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Senior Manager
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right, that was a typo on my part.
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