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August 29, 2014

August 29, 2014

Posted by **Da S** on Monday, March 26, 2012 at 9:32am.

- Math -
**Reiny**, Monday, March 26, 2012 at 10:00amlet the total distance be x km

her speed for first part = (1/5)x/1 km/h = x/5 km/h

speed for second part = 180/4 = 45 mph

remaining distance = x - (1)(x/5) = 4x/5

so, 4(45) = 4x/5

180 = 4x/5

4x = 900

x = 225

the total trip was 225 km

her speed in the first part = x/5 = 225/5 = 45 km/h

the whole trip took 5 hrs

average speed for whole trip was 225/5 = 45 km/h

check:

whole trip = 225 km

first part = 225-180 = 45 km

1/5 of 225 = 45 km, check!

speed = 45/1 = 45 km/h , check!

second part of trip = 180 km

speed = 180/4 = 45 km/h

total time = 1 + 4 = 5 hrs/, check!

average speed for whole trip = 225/5 = 45 km/h

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