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secondary 3 | A Maths
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Candice Tan
Candice Tan

secondary 3 chevron_right A Maths chevron_right Singapore

Averages

I got up to re arranging the formulas and substituting them but I don’t really know where to go from there and whether or not it was the right approach

Date Posted: 4 years ago
Views: 195
Eric Nicholas K
Eric Nicholas K
4 years ago
For this type of questions, the elimination approach is much more efficient than the substitution approach.

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Eric Nicholas K
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Candice Tan
Candice Tan
4 years ago
Thank you so much!! I appreciate the help and the clear working out, this was really helpful
J
J
4 years ago
Similar questions have actually appeared in the P6 curriculum,
Here's a faster alternative method without the need for any equations or eliminations :
Part i)
Average of 1st and 2nd = 72
So 1st + 2nd = 72 x 2 = 144
Average of 3rd and 4th = 77
So 3rd + 4th = 77 x 2 = 154
Average of 5th and 6th = 79
So 5th + 6th = 79 x 2 = 158
Total of 1st to 6th = 144 + 154 + 158 = 456
Overall Average = 456 ÷ 6 = 76

Part ii)
Average of 2nd and 3rd = 75
So 2nd + 3rd = 75 x 2 = 150
Average of 4th and 5th = 78
So 4th + 5th = 78 x 2 = 156
So 1st + 6th = Total - (2nd + 3rd) - (4th + 5th)
= 456 - 150 - 156 = 150
Average of the 1st and 6th = 150 ÷ 2 = 75
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