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Which of the following number is not the
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06 May 2017, 11:28
06 May 2017, 11:28
1
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Question Stats:
81% (02:05) correct
18% (02:30) wrong based on 11 sessions
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Which of the following number is not the sum of three consecutive odd numbers?
1) 15
2) 75
3) 123
4) 297
5) 313
Is there any shortcut technique to approach this question such as with prime factorization or something?
thanks
1) 15
2) 75
3) 123
4) 297
5) 313
Is there any shortcut technique to approach this question such as with prime factorization or something?
thanks
Re: Which of the following number is not the
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06 May 2017, 16:42
06 May 2017, 16:42
3
Expert Reply
Explanation
Its given that the number must be sum of 3 consecutive odd numbers. Then the numbers must be around 1/3 the original number
1) 15 So \(\frac{15}{3}\) =5, so the three consecutive odd numbers \(3+5+7 =15\)
2) 75 So \(\frac{75}{3}\) =25, so the three consecutive odd numbers \(23+25+27 =75\)
3) 123 So \(\frac{123}{3}\) =41, so the three consecutive odd numbers \(39+41+43 =123\)
4) 297 So \(\frac{297}{3}\) =99, so the three consecutive odd numbers \(97+99+101 =297\)
5) 313 Must be correct!
Its given that the number must be sum of 3 consecutive odd numbers. Then the numbers must be around 1/3 the original number
1) 15 So \(\frac{15}{3}\) =5, so the three consecutive odd numbers \(3+5+7 =15\)
2) 75 So \(\frac{75}{3}\) =25, so the three consecutive odd numbers \(23+25+27 =75\)
3) 123 So \(\frac{123}{3}\) =41, so the three consecutive odd numbers \(39+41+43 =123\)
4) 297 So \(\frac{297}{3}\) =99, so the three consecutive odd numbers \(97+99+101 =297\)
5) 313 Must be correct!
Re: Which of the following number is not the
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31 Oct 2019, 06:17
31 Oct 2019, 06:17
1
First I chose an incorrect answer, and only after that realized that it can solved using properties of numbers. I'm not sure in my solution, but here it is.
Three consecutive odd numbers can be written as
n + n+2 + n+4 = 3n+6
If we subtract 6 from the numbers given, the resulting integer must be a multiple of three:
15-6=9 works
75-6=69 works
123-6=117 works
297-6=291 works
313-6=307 does not work - correct answer
Three consecutive odd numbers can be written as
n + n+2 + n+4 = 3n+6
If we subtract 6 from the numbers given, the resulting integer must be a multiple of three:
15-6=9 works
75-6=69 works
123-6=117 works
297-6=291 works
313-6=307 does not work - correct answer
