Discussion :: Odd Man Out and Series - Find Wrong No. (Q.No.7)
Find out the wrong number in the series.
| 7. | 1, 3, 10, 21, 64, 129, 356, 777 |
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Answer: Option E Explanation: A x 2 + 1, B x 3 + 1, C x 2 + 1, D x 3 + 1 and so on. So, 356 is wrong. |
| Nagendramurthy said: (Jun 20, 2011) | |
| Alternate method: 1=1 3=3 10=1+0=1 21=2+1=3 64=6+4=10=1+0=1 129=1+2+9=12=1+2=3 356=3+5+6=14=1+4=5( wrong one.. it should be 1) 777=7+7+7=21=2+1=3 Alternative 1 and 3 series.. this is method is correct.. |
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| Imran said: (Sep 21, 2011) | |
| a-1 and b=3 take first two number as a and b 1*2+1=3 3*3+1=10 10*2+1=21 21*3+1=64 64*2+1=129 129*3+1=388 but in the queston in 356 so 356 is worng 388*2+1=777 Is it clear 356 is wrong |
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| Sweety said: (Jan 24, 2014) | |
| 1, 3, 10, 21, 64, 129, 356, 777 3-1=2. 10-3=7. 21-10=11. 64-21=43. 129-64=65. 356-129=127. 777-356=421. Answer should be 129. Because after subtracting in all the case give prime number except in 129-64 case. |
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| Sarvani said: (Aug 5, 2016) | |
| 64 is a perfect square number, rest all are not. | |
| Kuldeep Choudhary said: (Nov 5, 2016) | |
| One more alternative method:-. Separate out even & odd place numbers as 3, 21, 129, 777 & 1, 10, 64, 356. Then find the difference between each other like 18, 108, 548 & 9, 54, 292. Hereafter you will find the division of numbers are constant (i.e. Dividend=6), only 292 differs, then back this & 356 is the answer. |
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| Ankush said: (May 27, 2017) | |
| Agree @Imran. | |
| Anu said: (Aug 2, 2017) | |
| Thanks for the explanation. | |
| Pradyumna said: (Sep 1, 2017) | |
| Thanks for the answers. | |
| Aditya Kavlekar said: (Oct 28, 2018) | |
| As per my logic;. Only 10 is multiple of 5 and rest are not. So odd one is 10. |
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| Dhara said: (May 31, 2019) | |
| I think 64 should be the answer. We are adding prime no 1 3 7 11 13 so 64 is wrong. |
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