A person travels by car from one city to another with different constant speeds between pairs of cities. She drives for 50.0 min at 85.0 km/h, 8.0 min at 80.0 km/h, and 45.0 min at 30.0 km/h and spends 60.0 min eating lunch and buying gas.
(a) Determine the average speed for the trip.
km/h
(b) Determine the distance between the initial and final cities along the route.
km
A person travels by car from one city to another with different constant speeds between pairs of cities. ?
2020-09-09 12:16 pm
回答 (3)
2020-09-09 1:20 pm
(a)
Average speed for the trip
= [85.0 × (50.0/60) + 80.0 × (8.0/60) + 30.0 × (45.0/60) + 0 × (60.0/60)] / [(50.0/60) + (8.0/60) + (45/60) + (60/60)] km/h
= (85.0 × 50.0 + 80.0 × 8.0 + 30.0 × 45) / (50.0 + 8.0 + 45 + 60) km/h
= 6240/163 km/h
= 38.3 km/h
(b)
Distance
= [85.0 × (50.0/60) + 80.0 × (8.0/60) + 30.0 × (45.0/60) + 0 × (60.0/60)] km
= 104 km
Average speed for the trip
= [85.0 × (50.0/60) + 80.0 × (8.0/60) + 30.0 × (45.0/60) + 0 × (60.0/60)] / [(50.0/60) + (8.0/60) + (45/60) + (60/60)] km/h
= (85.0 × 50.0 + 80.0 × 8.0 + 30.0 × 45) / (50.0 + 8.0 + 45 + 60) km/h
= 6240/163 km/h
= 38.3 km/h
(b)
Distance
= [85.0 × (50.0/60) + 80.0 × (8.0/60) + 30.0 × (45.0/60) + 0 × (60.0/60)] km
= 104 km
2020-09-09 12:49 pm
d1 = 85*50/60 = 70.8 km
d2 = 80*8/60 = 10.7 km d3 = 30*45/60 = 22.5 km
d = d1+d2+d3 = 70.83+10.67+22.50 = 104.0 km
Vav = d/t = 104*60/(50+8+45+60) = 38.3 km/h
d2 = 80*8/60 = 10.7 km d3 = 30*45/60 = 22.5 km
d = d1+d2+d3 = 70.83+10.67+22.50 = 104.0 km
Vav = d/t = 104*60/(50+8+45+60) = 38.3 km/h
2020-09-09 12:27 pm
Convert minutes to hours
50 min = 5/6 hours
8 min = 8/60 hours = 2/15 hours
45 min = 3/4 hours
60 min = 1 hour
85 km/hr * 5/6 hr =>
85 * 5 / 6 km =>
425 / 6 km =>
70.8333333..... km
80 km/hr * 2/15 hr =>
80 * 2/15 km =>
16 * 2/3 km =>
32/3 km =>
10.666666.... km
30 km/hr * 3/4 hr =>
30 * 3/4 km =>
15 * 3/2 km =>
45/2 km =>
22.5 km
0 km/hr * 1 hr =>
0 km
5/6 hr + 2/15 hr + 3/4 hr + 1 hr =>
25/30 + 4/30 + 3/4 + 4/4 hr =>
29/30 + 7/4 hr =>
58/60 + 105/60 hr =>
163/60 hr
425/6 km + 32/3 km + 45/2 km + 0 km =>
425/6 + 64/6 + 135/6 + 0 km =>
(425 + 64 + 135) / 6 km =>
(489 + 135) / 6 km =>
624 / 6 km =>
104 km
Total trip distance: 104 km
Total trip time: 163/60 hr
104 km / (163/60 hr) =>
(104 * 60 / 163) km/hr =>
(6240 / 163) km/hr =>
38.28220858895705521472392638036... km/hr
38.3 km/hr is the average velocity.
50 min = 5/6 hours
8 min = 8/60 hours = 2/15 hours
45 min = 3/4 hours
60 min = 1 hour
85 km/hr * 5/6 hr =>
85 * 5 / 6 km =>
425 / 6 km =>
70.8333333..... km
80 km/hr * 2/15 hr =>
80 * 2/15 km =>
16 * 2/3 km =>
32/3 km =>
10.666666.... km
30 km/hr * 3/4 hr =>
30 * 3/4 km =>
15 * 3/2 km =>
45/2 km =>
22.5 km
0 km/hr * 1 hr =>
0 km
5/6 hr + 2/15 hr + 3/4 hr + 1 hr =>
25/30 + 4/30 + 3/4 + 4/4 hr =>
29/30 + 7/4 hr =>
58/60 + 105/60 hr =>
163/60 hr
425/6 km + 32/3 km + 45/2 km + 0 km =>
425/6 + 64/6 + 135/6 + 0 km =>
(425 + 64 + 135) / 6 km =>
(489 + 135) / 6 km =>
624 / 6 km =>
104 km
Total trip distance: 104 km
Total trip time: 163/60 hr
104 km / (163/60 hr) =>
(104 * 60 / 163) km/hr =>
(6240 / 163) km/hr =>
38.28220858895705521472392638036... km/hr
38.3 km/hr is the average velocity.
收錄日期: 2021-04-24 08:04:25
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20200909041630AA3lJrO