Two cars leave St. Louis from exactly the same spot at exactly the same time, one traveling west at 60 mph and the other traveling east at 40 mph. How long does it take before the cars are 180 miles apart?
2007-10-12 13:15:09 · 12 answers · asked by sarahbeth 4 in Science & Mathematics ➔ Mathematics
David f, I thought the same thing..lol!!!
2007-10-12 13:21:05 · update #1
if we consider speed is s and distance is d and time is t
so s=d/t or d=st
so for the 1st car d1=s1/t & for 2nd car d2=s2/t (t is one in both)
so d1+d2=s1*t +s2*t =(s1+s2)*t
180 =(60+40)*t=100*t
so t=180/100=1.8 hour
2007-10-12 13:27:36 · answer #1 · answered by mbdwy 5 · 0⤊ 0⤋
Since the cars are traveling in same direction, the combined speed is = 60 + 40 = 100mph
Since the time taken to be 180 miles apart, will be 180/100 = 1.8h
2007-10-12 13:22:54 · answer #2 · answered by ib 4 · 0⤊ 0⤋
Traffic is hell getting out of St. Louis. If they keep up at 40mph & 60mph, they'll probably cause a pile-up both ways on I-64. It'll take the tow truck drivers a half hour or so to get there, and they'll have to deal with traffic too, so even though the cars' speedometers say 40 & 60, they'll be crawling along at 15mph. Overall, it'll take about 7 hours (6 1/2 if the tow truck drivers don't stop for lunch).
2007-10-12 14:58:34 · answer #3 · answered by Expat Mike 7 · 1⤊ 0⤋
Their combined speed is 100 MPH.
180/100= 1.8 hours or 1 hour 48 minutes
2007-10-12 13:30:50 · answer #4 · answered by Dana 4 · 0⤊ 0⤋
[10]
1 hr 48 minutes
As the cars are moving away from each other,their relative speed is
60+40
=100 mph
Therefore,the cars will be 180 miles apart in
180/100
=1.8 hrs
=1 hr 48 minutes
2007-10-12 13:21:25 · answer #5 · answered by alpha 7 · 1⤊ 0⤋
distance = speed * time
the distance the first car travels in a certain amount of time plus the distance the second car travel in the same amount of time equals 180 miles
first car
d = 60t
second car:
40t
60t + 40t = 180
100t = 180
t = 1.8 hrs OR 1 hr and 48 min
2007-10-12 13:21:48 · answer #6 · answered by 7 · 0⤊ 0⤋
the speed difference between the cars is 100mph
100 for the first hour
the 80 is 4/5 of 100
so 4/5 of 60 is 48
so it is 1hour 48min
2007-10-12 13:24:20 · answer #7 · answered by elltea 4 · 0⤊ 0⤋
They are separating at a total speed of 100mph. Just divide 180 miles by 100mph, and you get 1.8 hours, which is 1 hour and 48 minutes (60 minutes x 0.8 = 48 minutes).
2007-10-12 13:24:18 · answer #8 · answered by TitoBob 7 · 0⤊ 0⤋
Two cars cannot occupy "exactly the same spot at the same time"
Assuming they leave at the same time from a negligible distance apart ...
:)
one is traveling 1.5miles faster than the other (ratio 3:2), therefore it will travel 1.5x for every x the 40mph travels
1.5 + 1 = 2.5
180/2.5 = 72
slow car travels 72 miles
72 miles @ 40mph =
1hr & 48minutes
ANS: 1hr and 48minutes
2007-10-12 13:20:15 · answer #9 · answered by David F 5 · 0⤊ 1⤋
60x - (-40x) = 180 miles
100x = 180 miles
x = 1.8 hours
0.8 * 60 = 48
1 hour 48 minutes
2007-10-12 13:24:19 · answer #10 · answered by Anonymous · 0⤊ 0⤋
if they go away from each other, just assume that one does not move and the other does, thus it would be as if one is stationary and the other travels at 100mph
the formula to calculate the distance after t time is d=vt so t=d/v
t=180/100=1.8 hours
1h0.8*60m
1h46m
2007-10-12 13:22:00 · answer #11 · answered by Maurizio G 2 · 0⤊ 1⤋