please help me to answer these question!
Time needed (in proportion) Distance traveled(in proportion)
Place A to B 2 4
Place B to C 5 3
If it took Mr.Chan 20 minutes to travel from Place B to C,and driving speed from Place A to B was 45km/hour.
(1)Find the distance from Place A to B.
(2)Find average driving speed for the whole journey.
maths f.1 hurry!help,please!
2007-03-30 6:43 am
回答 (1)
2007-03-30 8:40 am
✔ 最佳答案
(1)The distance from Place A to B
= speed x time
= 45 x ( 20 / 60 ) x ( 2 / 5 ) ( 除 60 因為單位是 hour , 2 / 5 是比例 )
= 6 km
(2)
Average driving speed for the whole journey
= total distance / total time
= [ 6 + 6 x ( 3 / 4 ) ] / [ ( 20 / 60 ) x ( 2 / 5 ) + ( 20 / 60 ) ]
= [ 6 + ( 9 / 2 ) ] / [ ( 2 / 15 ) + ( 1 / 3 ) ]
= ( 21 / 2 ) / ( 7 / 15 )
= ( 45 / 2 )
= 22.5 km/hour
收錄日期: 2021-04-12 20:22:37
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