數學小學88

貨車每小時行 =75km
單車每min行 =10m =10/1000=10000km
單車每小時行 =36km
30分鐘後兩車相距
=(75+ 36) x 1/2
= 55.5 km



2010-05-08 19:08:45 補充：
Sorry,
貨車每小時行 =75km
單車每min行 =10m
單車每小時行 =36km
30分鐘後兩車相距
=(75+ 36) x 1/2
= 55.5 km

貨車每小時行 =75km
單車每min行 =10m =10/1000=10000km
單車每小時行 =36km
30分鐘後兩車相距
=(75+ 36) x 1/2
= 55.5 km

貨車以75㏎/h = 75*30/60 = 37.5kM
單車以10m/s = 10*60*30/1000 = 18kM
= 37.5+18=55.5
30分鐘後兩車相距 = 55.5kM

Let O be the Origin,
Let point A be the lolly due to East,
Let point B be the bicycle due to West.

So AOB is a straight Line,

OA = 75kmh^-1 constantly 30min,
so OA = 37.5km

OB = 10ms^-1 constantly 30min,
so OB = 18km

Since AB = AO+OB,
So Therefore,AB = 55.5km,

So The distance between The lolly and the bicycle is 55.5km.

10x30x60/1000+75x0.5
=18+37.5
=55.5km

貨車每小時行 75公里,

單車每小時行 10m x 60秒 x 60分鐘 = 36000米, 即是 36公里每小時,

30分鐘後, 應是 (75+ 36) x 30/60 = 55,5 公里.

是不是這樣...