Data sets word problem

kidnik6

New member
Joined
Sep 3, 2012
Messages
8
This is the only question on my homework that I have no idea where to start. I'm probably making it harder than it really is. It states:

The scores of a student on the first seven of eight quizzes are: 62,68,50,58,58,54,70
A mean average of 54 on the eight quizzes is required to pass the course.
a.) What grade must she receive on the last quiz to pass the course?
b.) A quiz average of 61 is needed to get a B+ for this course. What grade must she receive on the last quiz to get a B+ for the course?
c.) Suppose the lowest quiz is dropped and the average is taken from the remaining seven quizzes. What grade must she receive on the last quiz to get a B+ for the course?


Any help is appreciated. Thank you!
 
Last edited:
Let x be the score in question, then add up all of the scores including the unknown, divide by 8 and equate to the desired average, then solve for x. What do you find?
 
So the sum of all eight numbers would be 420 + x. Therefor 420 + x/ 8 = 54 and x=12....? Or is this for part b, and I set it equal to 61 not 54?
 
You did part a) correctly, for part b) just replace 54 with 61 and solve for x...do you know what to do for part c)?
 
So the sum of all eight numbers would be 420 + x. Therefor 420 + x/ 8 = 54 and x=12....? Or is this for part b, and I set it equal to 61 not 54?
\(\displaystyle \dfrac{420 + x}{8} = 54 \implies 420 + x = 432 \implies x = 432 - 420 = 12.\)

12 is the correct answer for (a). It looks odd. But consider the average for the first seven quizzes:

\(\displaystyle \dfrac{62 + 68 + 50 + 58 + 58 + 54 + 70}{7} = \dfrac{420}{7} = 60.\)

The student is already way beyond the passing average on the first seven quizzes so even a rather horrible grade on the last quiz will still result in a pass. It is a useful trick to ask yourself whether an answer makes sense.
 
I think....You take the sum of 62,68,58,58,54,70 which is equal to 370. So 370+x/7 = 61. So x=57....?
 
Top