Question 830889: The average score of 4 students in a test was 60 marks. If the difference in scores between the top 3 students is 5 marks each, and the last student is 15 marks behind the 3rd student, how many marks did the last student receive?
Answer by JulietG(1812)   (Show Source):
You can put this solution on YOUR website! Let A be the top mark, B be the second, C be the third, and D be the bottom.
Here's what we're told in the problem:
(A + B + C + D)/4 = 60
or, A + B + C + D = 240 (I just multiplied each side by 4 to get rid of the fraction)
D = A - 5 - 5 - 15
C = A - 5 - 5
B = A - 5
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Now we can put those values into the original equation.
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A + (A-5) + (A-10) + (A-25) = 240
Add the As
4A -5 -10 -25 = 240
Do the subtraction
4A - 40 = 240
Add 40 to each side
4A = 280
Divide each side by 4
A = 70
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Let's plug it back in to the original question to prove it.
(A)70 + (B)65 + (C)60 + (D)45 does indeed equal 240.
Success!
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That must have been a very difficult exam!
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