GMAT Prep DS Question

Question

Please explain

bkk145 · Answer

(1) if n=98, sum = 9+8 = 17, then n is more than 80
if n=76, sum = 13, the n is less than 80
INSUFFICIENT

(2) Single digit primes are 2, 3, 5, 7
This means that the tens digit of n cannot be greater than 7; thus, n must be less than 80.
SUFFICIENT

r019h · Answer

St. 1
n= 1+1= 2 where n<80>80

INSUFF

St. 2
if both digits are prime, then tenth digit is less than 8, since greatest single digit prime is 7 which will make n< 80

SUFF

B

StartupAddict · Answer

B

check A first: 92 or 32, insuff.

then B: no numbers bigger than 80, so hence suff.

B

GMATBLACKBELT · Answer

Ohhhhh ok. I thought ur pic said the OA was C. I was sittin here like how can it be C??? S1: test out numbers above 80. We need them to add up to 11, 13, 17, etc... We can have 92 ---> 9+2 = 11. or 94 ---> 9+4 = 13 Insuff. S2: If both are prime and if n<99. Then the highest prime we can have for the tens and units digit is 77. Thus n < 80. Suff. B

GMAT Prep DS Question

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