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primary 6 | Maths
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Date Posted: 7 years ago
Views: 300
At first, boys = 3x girls
After 10 girls left, girls = girls -10
After 50 boys left, boys = (3x girls - 50), also (girls-10)/2.
3x girls - 50 = (girls- 10)/2
2x (3xgirls -50) = (girls -10)
6xgirls - 100 = girls - 10
(6girls - 100) - girls = (girls - 10) - girls
5girls - 100 = -10
5girls - 100 + 100 = -10 + 100
5girls = 90
Girls = 18
Boys = 3xgirls
=54
Together =18 + 54
= 62
After 10 girls left, girls = girls -10
After 50 boys left, boys = (3x girls - 50), also (girls-10)/2.
3x girls - 50 = (girls- 10)/2
2x (3xgirls -50) = (girls -10)
6xgirls - 100 = girls - 10
(6girls - 100) - girls = (girls - 10) - girls
5girls - 100 = -10
5girls - 100 + 100 = -10 + 100
5girls = 90
Girls = 18
Boys = 3xgirls
=54
Together =18 + 54
= 62
72
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done
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since it's an "at first" question, recommend working backwards. Thus, draw the model for the remaining students first ie. "twice as many girls as boys left in the library"
Date Posted:
7 years ago
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