A motorist travels for 3h at 80km/h amd 4h at 60km/h. What is her average speed for the trip?

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A) 74km/h
B)69 km/h
C)70km/h
D) cannot tell
C)140km/h

2007-07-22 18:14:49 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics

distance = rate * time

distance = 3*80 + 4*60 = 240 + 240 = 480

rate = distance / time = 480 / (3 + 4) = 480/7 ≈ 68.57 km/h

The answer is B.

2007-07-22 18:21:26 · answer #1 · answered by Northstar 7 · 0⤊ 0⤋

Rounded off, the answer is 69k/h.

2007-07-26 18:40:22 · answer #2 · answered by johnandeileen2000 7 · 0⤊ 0⤋

the answer is B...which is rounded from 68.571428

2007-07-23 01:26:51 · answer #3 · answered by Anonymous · 0⤊ 0⤋