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If r is divisible by 10 and s is divisible by 9, rs must hav
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12 Aug 2018, 15:41
12 Aug 2018, 15:41
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Question Stats:
85% (01:05) correct
14% (00:40) wrong based on 67 sessions
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If r is divisible by 10 and s is divisible by 9, rs must have at least how many factors?
(A) Two
(B) Four
(C) Twelve
(D) Fourteen
(E) Sixteen
(A) Two
(B) Four
(C) Twelve
(D) Fourteen
(E) Sixteen
Re: If r is divisible by 10 and s is divisible by 9, rs must hav
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15 Aug 2018, 08:19
15 Aug 2018, 08:19
1
Expert Reply
Explanation
This problem is most easily solved with an example. If r = 10 and s = 9, then rs = 90. The factors of 90 are 1 & 90, 2 & 45, 3 & 30, 5 & 18, 6 & 15, and 9 & 10. Count to get a minimum of 12 factors.
This problem is most easily solved with an example. If r = 10 and s = 9, then rs = 90. The factors of 90 are 1 & 90, 2 & 45, 3 & 30, 5 & 18, 6 & 15, and 9 & 10. Count to get a minimum of 12 factors.
Re: If r is divisible by 10 and s is divisible by 9, rs must hav
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31 Aug 2018, 08:56
31 Aug 2018, 08:56
3
RS is 90.. so in order to count the number of factors of 90 we need to see prime factorization of 90
we get 3*3*2*5
now we have 3 -- twice and 2 and 5 once
we add 1 to each of their power and multiple the power- 3*2*2= 12 hence the answer is C.
we get 3*3*2*5
now we have 3 -- twice and 2 and 5 once
we add 1 to each of their power and multiple the power- 3*2*2= 12 hence the answer is C.
