Aptitude - Problems on Numbers - Discussion
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Read more:"I never see what has been done; I only see what remains to be done."
- Marie Curie
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A two-digit number is such that the product of the digits is 8. When 18 is added to the number, then the digits are reversed. The number is:
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18 | [B]. |
24 | | [C]. |
42 | [D]. |
81 |
Answer: Option A
Explanation:
| Let the ten's and unit digit be x and |
8 |
respectively. |
| x |
| Then, |
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10x + |
8 |
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+ 18 = 10 x |
8 |
+ x |
| x |
x |
 10x2 + 8 + 18x = 80 + x2
9x2 + 18x - 72 = 0
x2 + 2x - 8 = 0
(x + 4)(x - 2) = 0
x = 2.
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Saradhapriyanka.S said:
(Wed, Aug 11, 2010 09:06:16 AM)
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| I could not understood your answer, please explain in some other way. |
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Chandra said:
(Tue, Aug 17, 2010 06:42:05 AM)
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There are only four two digit numbers whose product of the digits is 8. They are 18, 81, 24 and 42.
We can get easily 24 is the answer. |
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Sun said:
(Mon, Oct 4, 2010 04:19:01 AM)
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We can directly check out the answer through options.
24 + 18 = 42 which gives product 8. |
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Shanthi said:
(Sat, Oct 23, 2010 03:35:08 AM)
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| it is very simple..u can get ans from the options itself.18+18=36 no. not reversed. tak 24+18=42 no.reversed. 24 is reversed as 42 |
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Sudheer said:
(Sat, Feb 12, 2011 10:20:32 PM)
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Products of 8 is 2*4, 4*2, 8*1, 1*8.
But he is telling by adding 18 to it the digits are reversed means 24+18=42.
24 is changed to 42. So, the answer is 24. |
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May said:
(Sun, Apr 17, 2011 12:39:58 PM)
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| Oh.. u great and feeling in so easy.. thx u.. |
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Sunny said:
(Tue, Jul 5, 2011 02:49:08 PM)
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| Why didn't you take 8x, 1/x and solve the problem? |
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Manojit said:
(Mon, Feb 6, 2012 05:21:55 PM)
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Product of two digit means multiple of two digit.
Suppose two digit is x, y.
Then x*y=8
y=8/x
Now two digit is x, 8/x.
Then look the above problem. |
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