Arthur D. answered • 09/13/15

Effective Mathematics Tutor

(86+73+71+x+x)/5=80

86+73+71+2x=400

230+2x=400

2x=400-230

2x=170

x=170/2

x=85 is what she has to get on her final exam

Lauren H.

asked • 09/13/15Linh has obtained scores of 86, 73, and 71 on her midterm algebra exams. If the final exam counts twice as much as a midterm, what score must she make on her final exam to get an average score of 80?

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Arthur D. answered • 09/13/15

Effective Mathematics Tutor

(86+73+71+x+x)/5=80

86+73+71+2x=400

230+2x=400

2x=400-230

2x=170

x=170/2

x=85 is what she has to get on her final exam

Alexander B. answered • 09/13/15

Advanced Math and Science Tutoring and Test Prep online (SAT, ACT)

Hello Lauren,

Let's write the equation for unknown final score x considering that the average of 4 numbers is 80, thus the sum should be 80*4 = 320:

86+73+71+2x = 320

or in canonical form

2x+230=320

This linear equation can be easily solved either manually or using online Linear Equation Solver (http://examn8.com/LinearEquations.aspx). The solution for x:

x= 45 (final score)

Hope this may help.

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