Integers

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danjuma: Senior | Next Rank: 100 Posts; Posts: 89; Joined: Thu Aug 26, 2010 9:29 am; Thanked: 4 times

by danjuma » Thu Oct 14, 2010 3:14 pm

If n is an integer between 10 and 99, is n < 80?

a.The sum of the 2 digits of n is prime number

b.Each of the 2 digits of n is a prime number

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Source: Beat The GMAT — Data Sufficiency | Thu Oct 14, 2010 3:14 pm

nisha.menon294: Senior | Next Rank: 100 Posts; Posts: 44; Joined: Sat Apr 10, 2010 8:33 am

by nisha.menon294 » Thu Oct 14, 2010 6:14 pm

is it c ?

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ksundar: Junior | Next Rank: 30 Posts; Posts: 25; Joined: Sun Dec 06, 2009 8:50 am; Thanked: 1 times

by ksundar » Thu Oct 14, 2010 6:20 pm

If we take the first statement, It is in sufficient because 98 is 9 + 8 = 17, is a prime number and 16 is 1+6=7 is a prime number. So we cannot prove that n < 80. Not sufficient.

Second statement, if n > 80, every number should have a 8 and a 9. Numbers 8 and 9 are not prime numbers, so anything greater than 80 cannot be the value of n. Sufficient.

IMO answer is B

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