文字方程式(英文)

2009-11-10 5:34 am

Two cars A and B 250 km apart are travelling towards each other on the same road.The travelling speed or car B is 5km/h more than 5 over 7 of the speed of car A.They will meet after 2 hours.Find the travelling speed of each.

請列明步驟

ps:以上的5 over 7係 7分之5 既意思

更新1:

點解2[x + (5x/7 + 5)] = 250會變做12x/7 + 5 = 125? 拆括號之後唔係2x+10x/7+10=250?

回答 (1)

用戶9112

2009-11-10 5:47 am

✔ 最佳答案

Let the speed of car A be x km/h
Then the speed of car B = (5x/7 + 5) km/h
In 2 hours' time, total distance travelled = 2[x + (5x/7 + 5)] = 250
12x/7 + 5 = 125
x = 70
Speed of car A = 70km/h
Speed of car B = (5/7)(70) + 5 = 55km/h

2009-11-09 22:53:43 補充：
2[x + 5x/7 + 5] = 250
x + 5x/7 + 5 = 125兩邊除以2
7x/7 + 5x/7 + 5 = 125
12x/7 + 5 = 125...

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