Saranya K.

asked • 09/11/15

Calculation query

Hi,
I have a query regarding calculation.Please help me out.
There are 3 exams
Exam1 is out of 30 -In this student obtained 26
Exam 2 is out of 30 -In this student obtained 24
Exam 3 is out of 100 -In this student obtained 70

By combining all these exam marks,we need results out of 50.
Method1:
Converting Exam1 marks to 10% (i.e) 8.67
Converting Exam2 marks to 10% (i.e) 8
Converting Exam3 marks to 30% (i.e) 21
----------------------------------------------------
Marks total: 37.67
so overall 50%(10%+10%+30%)

Method 2:
Converting Exam1 marks to 100% (i.e) 86.7
Converting Exam2 marks to 100% (i.e) 80
Converting Exam3 marks to 100% (i.e) 70
----------------------------------------------------
Marks total: 236.7( out of 300)
Converting to 100: 78.6
Converting to 50 : 39.3


Why the results is varying by these two methods.Please clarify us and tell us which is the correct method.

3 Answers By Expert Tutors

By:

Arthur D. answered • 09/11/15

Effective Mathematics Tutor

Arthur D.

tutor
Saranya,
            Also, in the first method the 70/100 is a lower score than the 26/30 or the 24/30. That's why when you weight the 70/100, you get a lower average than the average in the second method. The weighted 70/100 brings the average down.
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09/11/15

Alexander B. answered • 09/11/15

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

Jon P. answered • 09/11/15

Knowledgeable Math, Science, SAT, ACT tutor - Harvard honors grad

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