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collection of tough problems from G PREP - 22

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by abhasjha » Sat Feb 06, 2010 5:41 am
If k is a positive integer and the tens digit of k+5 is 4, what is the tens digit of k?

1) k > 35

2) The units digit of k is greater than 5.
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Source: — Data Sufficiency |

by harsh.champ » Sat Feb 06, 2010 6:08 am
abhasjha wrote:If k is a positive integer and the tens digit of k+5 is 4, what is the tens digit of k?

1) k > 35

2) The units digit of k is greater than 5.
Statement 1 alone :- k can range from 36 to 44.[k+5 ranges from 40 to 49]So, ten's digit cannot be determined.Though this statement was not needed and it was self-evident from the question only.
Statement 2 alone :-if units digit of k is greater than 5.Hence k can be 36,37,38,39.So, tens digit will be 3.

IMO B is the answer.
Last edited by harsh.champ on Sat Feb 06, 2010 3:12 pm, edited 1 time in total.
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by sanju09 » Sat Feb 06, 2010 6:19 am
abhasjha wrote:If k is a positive integer and the tens digit of k+5 is 4, what is the tens digit of k?

1) k > 35

2) The units digit of k is greater than 5.
When the tens digit of k + 5 is 4, the smallest k is 35.

(1) Now, when k > 35, there are so many cases when the tens digit of k + 5 is 4, which include 36 + 5 = 41 and 40 + 5 = 45. Insufficient

(2) This sounds same as info in (1) but is still different. We cannot take 40, 41, 42, 43, 44, and 45 for k now, and k = 46 onwards won't prove that the tens digit of k + 5 is 4 until we reach to the ranges 136 to 139, 236 to 239....2036 to 2039...., and in all these ranges for k, the tens digit of k remains to be 3 only. Sufficient

[spoiler]B[/spoiler]
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by ajith » Sat Feb 06, 2010 9:08 am
abhasjha wrote:If k is a positive integer and the tens digit of k+5 is 4, what is the tens digit of k?

1) k > 35

2) The units digit of k is greater than 5.
Tens digit of k+5 is 4 which itself implies that
34<k<45

1.) tens digit can either b 3 or 4 - doesnt help at all ; Insufficient
2) units digit of k is greater than 5 - helps to conclude that tens digit of k is 3. (all the possible values with ten's digit 4 has units digit less than 5) - sufficient

[spoiler]B IMO - Posting only this part, doesn't help other than to increase the post count[/spoiler]
Always borrow money from a pessimist, he doesn't expect to be paid back.
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by akahuja143 » Sat Feb 06, 2010 1:09 pm
My Pick would be B..
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by abhasjha » Mon Feb 08, 2010 12:36 am
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