Cherise scored 85 on her last math exam of 100 questions. Her teacher has an unusual way of scoring this test. He calculated her score by subtracting 2 times the number of wrong answers from the number of correct answers. If Cherise answered all 100 questions, how many did she get correct?
Asked
Active
Viewed 110 times
1
-
Let $x$ be the number of correct answers. Can you form an equation to get $85$? – Macavity Mar 18 '14 at 03:43
-
Still kinda confused with what equation should use. – user136159 Mar 18 '14 at 03:45
4 Answers
0
$x =$ # of wrong answers, $y =$ # of correct answers $\implies y - 2x = 85$, and $x + y = 100$. So $$y - 2(100 - y) = 85 \implies 3y = 285 \implies y = 285/3 = 95$$
Yiyuan Lee
- 14,435
DeepSea
- 77,651
0
score = correct - 2*(wrong)
85 = c-2w
but we have c+w=100 so, c=100-w and therefore;
85=100-w-2w
-15=-3w
w=5
Cherise answered 5 questions with the wrong answer.
0
Let the number of correct answers be $x$. Then the number of incorrect answers is $100 - x$. Thus,
$$x - 2(100 - x) = 85$$
Manipulate and solve directly for $x$, i.e. the number of correct answers.
Yiyuan Lee
- 14,435