For anyone less math-savvy like myself, this problem was surprisingly simple. I just used some logic:
"Of those who lost the first round, 7 also lost the second round." => 7 teams lost
both round 1 and round 2. At least 7 teams lost in the first round, too.
"How many teams won both games?"
Think about how competitions work!"None of the games resulted in a tie." =>
that means every team won, or lost. If 7 teams
lost in the second round, that means
7 other teams (the ones the losers competed against)
won in that second round.
If those same 7 teams lost both times, it's a logical step to
infer that 7 other teams also won both rounds, since
every loss also has a win.
That's all I used to complete this problem. Sure, you can call it a stretch without the underlying, precise math (you could argue at least one of those other teams lost round one but won round two, or vice versa), but the time saved was a worthwhile risk for me.
Sajjad1994
A soccer competition consisted of two rounds. In each round, the 20 teams competing were divided randomly into 10 pairs, and each pair played a single game. None of the games resulted in a tie, and of the teams that lost in the first round, 7 also lost in the second round. How many teams won both of their games?
(A) 3
(B) 4
(C) 5
(D) 6
(E) 7