Brain Teasers
Taking a Test
Robert took a test of 20 questions. The test was graded by giving 10 points for each correct answer and deducting 5 points for each incorrect answer. Robert answered all 20 questions and received a score of 125. How many wrong answers did he have?
Answer
He had 5 wrong answers. If he had answered all 20 questions correctly, he would have scored 200. Since he scored 125, this means he lost 75 points. We must deduct 15 points for each wrong answer; 10 points that he did not earn for getting it right, plus the 5 points that are deducted for the answer being wrong. 75 lost points divided by 15 equals 5 wrong answers.Hide Answer Show Answer
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Comments
This one took a sec to get. But I got it without looking yeah for me lol.
I found it easier just to let C=# correct answers.
Then 20-C=# wrong answers
So 10C-5(20-C)=125
Hence C=15
Then 20-C=# wrong answers
So 10C-5(20-C)=125
Hence C=15
Well I got it wrong silly me... nice one though
Yes, CMS, that would work too. Glad you guys liked it.
Whoa that's E-A-S-Y! So obvious, but still good!
Nice one. I too solved it by equations
X+Y= 20 & 10X-5Y=125 but the solution given is more elegant
X+Y= 20 & 10X-5Y=125 but the solution given is more elegant
I was going to solve by equations, but my initial guesses were right. Pretty easy...
Damn easy. How is this accepted as a BRAIN teaser???????????
I have to agree that it was far too easy, but I worked it out by taking the highest possible answer, subtracting the answer recieved and dividing the remainder by 15 (15= amount less than the possible score -5 +(-10))
Some of them have to be easy so the younger Brainglers can have stuff they can solve.
The trick that no-one has spotted so far is the cheating going on. Tim took the test but Robert did the answers. Cool!
Pretty easy, I thought.
The brainteaser was good and interesting, but there are many others like it.
The brainteaser was good and interesting, but there are many others like it.
Sure you need some easier teasers, but at some point it stops being a teaser. At best this one is close to that line.
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