Class has 50 question test, each correct answer is 2 pt, each wrong is -.5, if no answer then no points. If student needs to earn 70 pt on the test then what is the equation in terms of incorrect answers
Stacey Warren - Expert brainly.com
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number correct = x number incorrect = 50-x
when all correct x = 50 ; points = 100
when all incorrect 50*(-0.5) = -25 points
to get 70 points 2x -0.5(50-x)= 70
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the number of test question = 50
if you put in 50 for x then its 2x-.5(0)? which is 100 if you replace x with 50
So if 50 questions are all correct, then 50 (2) = 100
if 50 questions are all wrong, then 50 (-.5) = -25
So x = # of right questions, y = # of wrong questions
2x -.5y = 70
MY number I will say you will need x=38 and y =12
2 (38) - .5 (12) = 70
76 - 6 = 70
So the student needs at least 38 right and 12 wrong to get 70 points
DN_20 how did you know to use 38 and 12?
So let see:
(1)2x -.5y = 70
(2)x + y = 50
Multiply the (1) by 2
4x - y = 140
x +y = 50
Eliminate y, add the rest
5x = 190
x = 38
Plug in x:
38 +y = 50
There we go!!!!!!
looks great. but what is the equation in terms of incorrect answers. Shouldnt it be equal to 30 not 70 to focus on incorrect possibles?
Ok, so this is just the same:
(1)2x -.5y = 30
(2)x + y =50
So the same, you multiply (1) by 2
So 4x - y = 60
x+y = 50
Eliminate y, add the others:
5x = 110
x = 22
So y = 50 -22 =28
They will need 16 correct and 34 wrong
2 (22) -.5 (28)= 44-14= 30