請幫忙計算列式(最緊要列式)

candy7_fong

2008-05-31 9:55 pm

1) Mrs chan walks at 0.9 m/s How long will it take her to walk 54 m and back?

2) Two cars are approaching each othe from two places Town A and TownB 350km apart, at 65 km/h and 75km/h respectively.
a. How long will it take them to meet?
b. How far from Town B will their meeting place be?

3) In a race Car A and Car B were driing at 100 km/h and 80 km/h respectively . Car B started 1 h earlier. How long will it take A to overtake B?

回答 (1)

Matthew

2008-05-31 10:15 pm

✔ 最佳答案

1) The time taken for Mrs Chan to walk 54m and back
= (54 *2) / (0.9)
= (108) * (10 / 9)
= 12 * 10
= 120 s

2a) The time taken for them to meet
= (350) / (65 + 75)
= (350) / (140)
= (5/2) hours (或者 2.5 hours)

2b) The distance between Town B and their meeting place
= (2.5)(75)
= (375/2) km (或者 187.5 km)

(我唔肯定2b...係TownB出發個架既車速係 65km/h 定係 75km/h?
應該係車速 75km/h 個架
以上既列式假設左係車速75km/h 個架
以防萬一，如果係車速 65km/h 個架，則如下)

2b) The distance between Town B and their meeting place
= (2.5)(65)
= (325/2) km (或者 162.5 km)

3) The distance between Car A and B when Car A starts
= (80) * (1)
= 80 km

The rate of shortening of the distance between Car A and Car B
= 100 - 80
= 20 km/h

The time taken for Car A to overtake B
= (80/20)
= 4 hours

參考: me

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