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Wednesday, December 13 2017 @ 04:51 PM CST
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By: drstevewu (offline)  Wednesday, April 06 2016 @ 11:02 AM CDT (Read 1845 times)  
drstevewu

Hi , please help the following question:

1. The average score of all the children in a class for a test is 83 marks. The average score of all the 10 girls in the class is 90 marks. The average score of the boys is 78 marks.
(i) How many boys are there in the class?
(ii) Find the difference in the total scores between the boys and the girls?






Thank you,

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By: echeewh (offline)  Thursday, April 07 2016 @ 12:51 AM CDT  
echeewh

Hey <drstevewu>,

Following is my worked solution:

Let the number of boys be 1u.

Total number of children (Boys + Girls) = u + 10

Total marks of all children = (u + 10) × 83
= 83u + 830 -- (1)

Total marks of all boys (B ) = (u) × 78 = 78u

Total marks of all girls (G) = 10 × 90 = 900

B + G = 78u + 900 -- (2)

But (1)=(2), hence ...

83u + 830 = 78u + 900
83u - 78u = 900 - 830
5u = 70
u = 14

(i) 14 boys

(ii)
B - G (scores) = 78u - 900
= (78 × 14) - 900 = 1092 - 900
= 192

=======

Trust this helps.

Do let me know again if this is different from your <Anskey> or if there's further clarification.

Cheers,
Edward

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By: drstevewu (offline)  Sunday, April 10 2016 @ 07:33 PM CDT  
drstevewu

Thank you very much Edward.

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