An executive drives from Office A to Office B, a distance of 120 miles, at a constant spee… — GMAT

An executive drives from Office A to Office B, a distance of $120$ miles, at a constant speed of $40$ miles per hour. After spending exactly $1$ hour at Office B for a meeting, she returns to Office A along the exact same route at a constant speed of $60$ miles per hour. What is her average speed, in miles per hour, for the entire round trip including the time spent at Office B?

A
$35$
$40$ Cevap
C
$45$
D
$48$
E
$50$

Cevap

The average speed for the entire round trip, including the meeting time, is

40

miles per hour.

To find the average speed for the entire trip, divide total distance covered by total time elapsed. The total distance is

120 + 120 = 240

miles. The travel time outbound is

120 / 40 = 3

hours, and the travel time return is

120 / 60 = 2

hours. Including the

1

-hour meeting at Office B, the total elapsed time is

3 + 1 + 2 = 6

hours. Thus, the overall average speed is

240 / 6 = 40

miles per hour.

Adım Adım Çözüm

Calculate the travel time for the outbound leg from Office A to Office B.

\text{Time}_{\text{outbound}} = \frac{120\text{ miles}}{40\text{ mph}} = 3\text{ hours}

Time equals distance divided by speed.

Calculate the travel time for the return leg from Office B to Office A.

\text{Time}_{\text{return}} = \frac{120\text{ miles}}{60\text{ mph}} = 2\text{ hours}

Time equals distance divided by speed.

Determine the total distance and total elapsed time for the entire trip.

\text{Total Distance} = 120 + 120 = 240\text{ miles}

;

\text{Total Time} = 3\text{ hours (outbound)} + 1\text{ hour (meeting)} + 2\text{ hours (return)} = 6\text{ hours}

Average speed requires total distance divided by total time elapsed, which must include non-moving meeting time.

Calculate the overall average speed.

\text{Average Speed} = \frac{240\text{ miles}}{6\text{ hours}} = 40\text{ miles per hour}

Divide total distance by total time.

Anahtar Kavram

Average Speed for Multi-Leg Journeys

Tahmini Süre:2m 0s

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