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標題: pls help- maths [打印本頁]

作者: janetlam74 時間: 14-11-2 11:44 標題: pls help- maths

本帖最後由 janetlam74 於 14-11-2 12:10 編輯

pls help - maths( steps and answer).........thank you!!!!

1.) Two months ago, the total weight of Leo and Wilson was 130 kg. They went to a fitness centre together for physical training.
Now, the weight of Leo drops by 1/4 and the weight of Wilson drops by 2/7.
If Leo weight 5 kg less than Wilson at present,
what were their respective weight two months ago?

作者: bluesky999 時間: 14-11-2 12:27 標題: hi

本帖最後由 bluesky999 於 14-11-2 16:34 編輯

Let P be Peter's weights two months ago
(130-P)be John's weight two months ago.
(1-1/4)P+5=(1-2/7)(130-P)
3P/4+5=5/7(130-P)
21P+140=20(130-P)
21P+140=2600-20P
21P+20P=2600-140
41P=2460
P=60
Peter's weights two months ago is 60.
John's weights two months ago is 130-60=70

作者: tiger789 時間: 14-11-2 14:04

本帖最後由 tiger789 於 14-11-2 14:10 編輯

回覆 janetlam74 的帖子

X + Y = 130
3X/4 + 5 = 5Y/7

3X/4 + 5 = 5(130 - X)/7
21X/4 + 35 = 5(130 - X)
21X + 140 = 20(130 - X)
41X = 2460
X = 60

Y = 70

作者: Daddle 時間: 14-11-5 12:32

回覆 bluesky999 的帖子

Leo and Wilson changed to Peter and John?

作者: bluesky999 時間: 14-11-5 21:26

回覆 Daddle 的帖子

我仔份試卷是Peter and John.莫非唔同學校?出同一提數學?

作者: dubbies 時間: 14-11-5 21:48 標題: 回覆：pls help- maths

出一個q bank 有學校改少少當自己出。不過要留意中一做就係一個未知數中三教左二元方程先可設x同y

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