A vehicle-testing laboratory measured the distance a car travels after

Question

https://gmatclub.com/forum/download/file.php?id=89957 A vehicle-testing laboratory measured the distance a car travels after its brakes are applied at different speeds. The graph shows the car’s braking distance, in meters, for speeds from 20 kilometers per hour through 100 kilometers per hour. Before the brakes are applied, the car also travels some distance during the driver’s reaction time. At a speed of v kilometers per hour, the reaction distance, in kilometers, is \frac{v}{3600} . The car’s total stopping distance is the sum of its reaction distance and braking distance. From each drop-down menu, select the option that creates the most accurate statement based on the information provided. At 80 kilometers per hour, the car’s total stopping distance, rounded to the nearest 10 meters, is GRAPH_1_PLACEHOLDER . The average rate of change of braking distance from 30 to 50 kilometers per hour is approximately GRAPH_2_PLACEHOLDER the average rate of change from 70 to 90 kilometers per hour. GMAT-Club-Forum-fjk188nf.png

Bunuel · Accepted Answer

https://gmatclub.com/forum/download/file.php?id=89957

A vehicle-testing laboratory measured the distance a car travels after its brakes are applied at different speeds. The graph shows the car’s braking distance, in meters, for speeds from 20 kilometers per hour through 100 kilometers per hour.

Before the brakes are applied, the car also travels some distance during the driver’s reaction time. At a speed of v kilometers per hour, the reaction distance, in kilometers, is  \frac{v}{3600} .

The car’s total stopping distance is the sum of its reaction distance and braking distance.

From each drop-down menu, select the option that creates the most accurate statement based on the information provided.

At 80 kilometers per hour, the car’s total stopping distance, rounded to the nearest 10 meters, is  GRAPH_1_PLACEHOLDER .

The average rate of change of braking distance from 30 to 50 kilometers per hour is approximately  GRAPH_2_PLACEHOLDER  the average rate of change from 70 to 90 kilometers per hour.

Official Solution:

Drop-down 1

At 80 kilometers per hour, the graph shows a braking distance of about 50 meters.

The reaction distance is:

\frac{80}{3600}  km ≈ 0.022 km

Converting to meters:

0.022 * 1,000 ≈ 22 meters

Therefore, the total stopping distance is approximately:

50 + 22 = 72 meters

Rounded to the nearest 10 meters, this is  70 meters .

Answer: 70 meters

Drop-down 2

From 30 to 50 kilometers per hour, the braking distance increases from about 7 meters to about 19 meters, an increase of about 12 meters.

From 70 to 90 kilometers per hour, it increases from about 37 meters to about 62 meters, an increase of about 25 meters.

The two speed intervals have the same width, so their average rates of change can be compared by comparing these increases.

Since 12 is approximately one-half of 25, the first average rate of change is approximately  one-half of  the second.

Answer:  one-half of

Correct answer:

Drop-down 1: "70 meters"
Drop-down 2: "one-half of"

hd29 · Answer

1. At 80km/hr braking distance = 50m
And, reaction distance = 80x 1000/3600 = 200/9 = 22.2m

Total = 72.2m

2. Change in braking distance from 30km/hr to 50km/hr = 15m

And, change in distance from 70 to 90km/hr = 35m

So, it is one half.

A vehicle-testing laboratory measured the distance a car travels after

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A vehicle-testing laboratory measured the distance a car travels after

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