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If set S consists of all positive integers that are multiple
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04 Oct 2018, 16:47
04 Oct 2018, 16:47
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If set S consists of all positive integers that are multiples of both 2 and 7, how many numbers in set S are between 140 and 240, inclusive?
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Re: If set S consists of all positive integers that are multiple
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20 Nov 2018, 10:08
20 Nov 2018, 10:08
hi can you please expalin this?
Re: If set S consists of all positive integers that are multiple
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20 Nov 2018, 13:21
20 Nov 2018, 13:21
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asfandiar wrote:
hi can you please expalin this?
A positive integer that is a multiple of both 2 and 7 is a multiple of 14. Since 140 is a multiple of 14, start listing there and count the terms in the range: 140, 154, 168, 182, 196, 210, 224, 238.
Alternatively, note that 140 is the 10th multiple of 14, and 240/14 ≈ 17.143 (use the calculator).
Therefore, the 10th through the 17th multiples of 14, inclusive, are in this range. The number of terms is 17 – 10 + 1 = 8 (“add one before you are done” for an inclusive list).
