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Ipatiy [6.2K]
2 years ago
12

FOR 14 POINTS Thalia, a quiz show contestant, answered 20 questions. She was awarded 2 points for every correct answer that she

gave, but she was penalized 1 point for every incorrect answer. In the end, Thalia had a total of 28 points. In order to determine the number of correct and incorrect answers that she gave, a viewer at home used the system of linear equations x + y = 20 and 2 x + y = 28, with x being the number of correct answers and y being the number of incorrect answers. The viewer solved the system by using the linear combination method as shown. x + y = 20. + StartFraction Negative 2 x minus y = negative 28 over Negative x = negative 8 EndFraction. StartFraction negative x Over negative 1 EndFraction = StartFraction negative 8 Over negative 1 EndFraction. X = 8. 8 + y = 20. 8 + y minus 8 = 20 minus 8. y = 12. The viewer calculated that the contestant answered 8 questions correctly and 12 questions incorrectly. What went wrong? The viewer mistakenly determined that one of the equations in the system should be x + y = 20.Instead modifications should have been made before applying the equation. The viewer mistakenly determined that one of the equations in the system should be 2 x + y = 28. Instead modifications should have been made before applying the equation. The viewer multiplied the equation 2 x + y = 28 by –1 incorrectly. The viewer added the equations x + y = 20 and Negative 2 x minus y = negative 28 incorrectly.
Mathematics
2 answers:
Svetradugi [14.3K]2 years ago
7 0

Answer:

<em>The viewer mistakenly determined that one of the equations in the system should be 2 x + y = 28. Instead modifications should have been made before applying the equation.</em>

Step-by-step explanation:

Given

Total Questions = 20

Total Points = 28

Correct Answers = +2 points

Incorrect Answers = -1 point

Required

Spot the error in the viewer's calculation

The viewer represents the correct answers with x and the incorrect ones with y.

This implies that

x + y = 20

Also, for every correct answers, she gets 2 points;

<em>This can be represented by 2x</em>

and for every incorrect answers, she gets -1 point

<em>This can be represented by -y</em>

This implies that

2x - y = 28

This is where the viewer made a mistake

The viewer's mistake is that; instead of subtracting total incorrect points from the correct points, the viewer added them together;

Solving further

2x - y = 28

x + y = 20

Add both equations together

2x + x + y - y = 28 + 20

3x = 48

Divide both sides by 3

\frac{3x}{3} = \frac{48}{3}

x = \frac{48}{3}

x = 16

Substitute x = 16 in x + y = 20

16 + y = 20

Subtract 16 from both sides

16 - 16 + y = 20 - 16

y = 20 - 16

y = 4

<em>This implies that the contestant answered 16 questions correctly and 4 questions incorrectly</em>

<em></em>

ANEK [815]2 years ago
5 0

Answer: A

Step-by-step explanation:

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