MonSama wrote:
If m, n, and p are three-digit integers and m + n = p, is the sum of the units digits of m and n at least 2 more than the sum of the tens digits of m and n?
(1) The tens digit of p is greater than the sum of the tens digits of m and n.
(2) The tens and units digits of p are equal.
Dear
MonSama,
I'm happy to respond.
As always, an excellent question from
MGMAT.
For discussion purposes, let's say that
m = ABC
n = DEF
p = JKL
where the capital letters represents digits (C is the one's digit of m, B is the ten's digit of m, etc.)
Statement #1: K > B + E
Well, this statement tells us a few things. First of all, it tells us that the sum of the one's digits, (C + F) > 10. We know this because the only way K would be more than the sum of (B + E) is that if something "carries" from the addition in the one's column. The sum of the one's digits is greater than 10, so a 1 "carries" into the ten's column, making K bigger. We also know that K is a single digit, K < 10. Well, if (B + E) is less than K, it must also be less than ten. Combining all the inequalities here, we get
(B + E) < K < 10 < (C + F)
This definitively answer the prompt question, so this statement, alone and by itself, is
sufficient.
Statement #2: K = L
Well, let's think about this ---
111 + 222 = 333 ---- here, (B + E) = (C + F)
217 + 138 = 355 ---- here, (B + E) < (C + F)
272 + 183 = 455 ---- here, (B + E) > (C + F)
With this constraint, we can make the two sums equal, or we can make either greater than the other. This constraint does not allow us to determine a clear unambiguous answer to the prompt question. This statement, alone and by itself, is
insufficient.
First statement sufficient, second, insufficient. Answer =
(A)Does all this make sense?
Mike