You can
put this solution on YOUR website!Mary needs to go to Jane’s house. Mary drives 4 mph going uphill, goes 6 mph
on flat ground and goes 12 mph downhill. It takes her 1 hour to do the trip.
How far is Jane’s house?
:
Let d = distance to house
;
Divide the distance into 4 + 6 + 12 = 22 units
:
The distance at each speed:
= .182d; distance at 4 mph
= .273d; distance at 6 mph
= .545d; distance at 12 mph
:
Write a time equation, Time = dist/speed
+
+
= 1
Clear the denominator multiply equation 12
3(.182d) + 2(.273d) + .545d = 12
:
.546d + .546d + .545d = 12
;
1.64d = 12
d =
d = 7.3 miles
:
Interesting that this is the same distance if you just averaged the 3 speeds
= 7.33 mi; in 1 hr, the distance would 7.33 mi
