SOLUTION: Help would be appreciated for the following question:
A coach driver has to travel 560 km. The driver A02 usually drives at an average speed of r km/h.
He can arrive 45 minutes e
Question 1039066: Help would be appreciated for the following question:
A coach driver has to travel 560 km. The driver A02 usually drives at an average speed of r km/h.
He can arrive 45 minutes earlier if he increases his average speed by 6 km/h. Find the value of r correct to the nearest whole number.
Thanks so much Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! A coach driver has to travel 560 km. The driver A02 usually drives at an average speed of r km/h.
He can arrive 45 minutes earlier if he increases his average speed by 6 km/h. Find the value of r correct to the nearest whole number.
:
r = the normal speed
then
(r+6) = the faster speed that gets him there 45 min earlier
:
Change 45 min to .75 hrs
:
Write a time equation; time = dist/speed
normal time - faster time = .75 hrs - = .75
multiply by r(r+6), cancel the denominators and you have
560(r+6) - 560r = .75r(r+6)
560r + 3360 - 560r = .75r^2 + 4.5r
form a quadratic equation on the right
0 = .75r^2 + 4.5r - 3360
Solve for r using the quadratic formula; a=.75; b=4.5; c=-3360
You should get a positive solution of
r= 64 km/hr is his normal speed
:
:
confirm this solution by finding actual time at each speed
560/64 = 8.75 hrs
560/70 = 8.00 hrs
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time dif: .75 hrs which is 45 min
