If you are planning to take a trip of 20 miles and average 30mile/hour but you find, due to traffic, that you have only averaged 15miles/hour for the first 10 miles, how fast will you need to go for the second 10 miles to meet your goal?
2007-06-20 12:45:47 · 4 answers · asked by MT 1 in Science & Mathematics ➔ Mathematics
Driving a 20 mile trip at 30mph takes you 40 minutes.
To cover 10 miles at 15mph, you'll also need 40 minutes. You still need to cover 10 miles, but have no time left.
So no matter how fast you could go, you would be late!
2007-06-20 12:53:01 · answer #1 · answered by Damien 4 · 0⤊ 0⤋
t= d/r so 10/15 = 2/3 hour for the first 10 miles.
To average 30mph you must travel 20 mile in 2/3 hour.
But you have alreday used up t
your 2/3 of an hour during the first 10 miles. Therefore it is impossible to average 30 mph for the entire trip.
2007-06-20 19:56:13 · answer #2 · answered by ironduke8159 7 · 0⤊ 0⤋
total distance to cover = 20 miles
original average speed planned = 30 miles/hr
time = distance/speed = 20/30 = 2/3hr = 2/3 * 60min = 40mins
for first distance = 10 miles
average speed = 15 miles/hour
time taken = distance/speed = 10/15 = 2/3 hr = 2/3 * 60min = 40mins
okay, it seems that I have used up the 40min deadline to reach my destination.
seriously?
I need a rocket now.
or the Night Crawler from X-Men to teleport me to my destination.
2007-06-20 20:22:37 · answer #3 · answered by jurassicko 4 · 0⤊ 0⤋
x=vt
20mi=30mi/hr . t
t=2/3 hr (your goal)
10 mi=15mi/hr . t1
t1=10/15hr=2/3hr(time used)
remaining t=2/3-2/3=0
v=x/t=10mi/0hr=infinity (mi/hr)
2007-06-20 19:57:04 · answer #4 · answered by Alberd 4 · 0⤊ 0⤋