F3 Maths Problems

(a)
The weight mean mark of Peter :
(70 × 2 + u × 2 + v × 1) / (2 + 2 + 1) = 68
(140 + 2u + v) / 5 = 68
140 + 2u + v = 340
2u + v = 200


(b)
Marks for Chinese and Mathematics tests are v and u respectively instead.
The weight mean mark becomes :
(70 × 2 + v × 2 + u × 1) / (2 + 2 + 1) = 72
(140 + 2v + u) / 5 = 72
140 + u + 2v = 360
u + 2v = 220
u = 220 - 2v ...... [1]

Put [1] into 2u + v = 200 :
2(220 - 2v) + v = 200
440 - 4v + v = 200
3v = 240
v = 80

Put v = 80 into [1] :
u = 220 - 2(80)
u = 60

Hence, u = 60, v = 80

2015-01-02 15:24:32 補充：
"The table on the right" should be "The table at the bottom".

"The table on the right"???

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