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計算速率 (小四題)數學謎題

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中文:小明每天走路上學。如果他走的速度是80米每分鐘,他會早6分鐘回校。如果他走的速度降為50米每分鐘,他會遲到3分鐘回校。問學校與家中的距離。
English: Ming Ming walks to school everyday. If he moves at the rate of 80 meters per minute, he could arrive at school 6 minutes too early. Should he move at 50 meters per minutem he would be late by 3 minute. How far away is the school from home?
arashilove2013-11-09提供(2013-11-09修改)
來源:小四的功課
看答案
Let speed be V, distance be S, Time be T
1) S = U1T1 = 80T1
2) S = U2T2 = 50T2
==> T+ 6 = T2 -3
Because T= T1 = 9
So T= T1 + 9

Subt T2 = T1 + 9, 8T1 = 5T2
So, 8T1 = 5 ( T+ 9 )
3T1 = 45
T1 = 15 min

Distance = (80) T1 = (80)(15) = 1200 m #

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