Jerry spent 2.5 h biking up Mount Lowe, rested at the top for 30 min., and biked down in 1.5 h. How far did he bike if his rate of ascent was 3km/h less than his rate of descent? (plz show ur work. I'm having trouble with this problem. Plz and thnx a lot!)
2007-11-04 16:54:00 · 3 answers · asked by Wendy F 1 in Science & Mathematics ➔ Mathematics
Uphill he travels x km/hr
Downhill he travels x+3 km/hr
distance = rate (time)
distance up = distance down
(x km/hr)(2.5hr) = (x+3 km/hr)(1.5hr)
2.5x = 1.5x + 4.5
2.5x - 1.5x = 4.5
x = 4.5 km/hr uphill
x + 3 = 7.5 km/hr downhill
Distance uphill = (4.5 km/hr)(2.5 hr)
Distance uphill = 11.25 km
Distance downhill = (7.5 km/hr)(1.5 hr)
Distance downhill = 11.25 km
note they are the same so the total distance travelled is
Total Distance = Distance uphill + Distance downhill
Total Distance = 2(11.25 km)
Total Distance = 22.5 km ANSWER
2007-11-04 17:10:43 · answer #1 · answered by Anonymous · 0⤊ 0⤋
have you heard of the triANGLE, distance / speed = time speed* time =distance and distance / time = speed. The speed was 3km/h, riding up took 2.5 h + riding down a total of 1.5 = a total of 4 h (time) *(speed) 3km/h = (distance) 12 km, them questions make it sound hard, hes naturally gonna ascent slow than he will desent, either way he still went up the to the same place he came down from , the 30 min rest he didnt move, so that doesnt need included in the equation. Hope this helps you.
2007-11-04 17:05:56 · answer #2 · answered by JD 3 · 0⤊ 0⤋
distances are equal, distance is rate(time)
d-up = d-down
(r - 3)(2.5) = r(1.5)
2.5r - 7.5 = 1.5r
1.0r = 7.5
d = (7.5)(1.5) = 11.25,
so total distance (up+down) = 22.5 km.
2007-11-04 17:02:13 · answer #3 · answered by Philo 7 · 0⤊ 0⤋