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 By: Rohana (offline)  Saturday, December 08 2012 @ 10:58 PM CST (Read 945 times)
Rohana

Q28. A group of 40 pupils took part in the Maths Olympiad competition. Their average score was 85 marks. The average score for the boys was 90 marks. The average score for the girls was 70 marks. How many girls participated in the competition?
Thanks!

Junior

Registered: 01/24/12
Posts: 18

 By: echeewh (offline)  Sunday, December 09 2012 @ 07:27 AM CST
echeewh

hi Rohana,

Following pls find my worked solution:

Total score = 40 × 85 = 3400

Let number of girls (G) = 1u; hence number of boys (B ) = 40 - 1u.

Total score (G) = 1u × 70 = 70u
Total score (B ) = (40 - 1u) × 90 = 3600 - 90u
Total score = 70u + 3600 - 90u = 3600 - 20u

Now we have ...

3600 - 20u = 3400
20u --> 3600 - 3400 = 200
1u --> 10

Hence, 10 girls participated in the competition

===============

Trust this helps.

Do let me know again if there's further clarification.

Cheers,
Edward

Active Member

Registered: 04/21/11
Posts: 627

 By: Rohana (offline)  Tuesday, December 11 2012 @ 05:37 AM CST
Rohana

Hi Edward,

Thankyou so much for the maths solution.

Regards
Rohana

Junior

Registered: 01/24/12
Posts: 18

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