A rocket is launched at 41,400 kilometers per hour. What is the speed of the rocket...

BTGmoderatorLU wrote: ↑

Thu Apr 09, 2020 4:58 am

Source: Economist GMAT

A rocket is launched at 41,400 kilometers per hour. What is the speed of the rocket in meters per second?

A. 115
B. 1150
C. 11,500
D. 69,000
E. 149,040

The OA is C

When I scan the answer choices (ALWAYS scan the answer choices before solving the question), I see that they are very spread apart, which means we can be aggressive with our estimation.

So rather than starting with a speed of 41,400 kilometers per hour, let's say the speed is approximately 36,000 kilometers per hour

Since there are 3600 seconds in an hour, we can all say that: 36,000 kilometers per hour = 10 kilometers per SECOND

Since there are 1000 meters in 1 kilometer, we can say: 10 kilometers per SECOND = 10,000 kilometers per SECOND

When we check the answer choices, only C is close to 10,000 kilometers per SECOND

Answer: C

Cheers,
Brent

BTGmoderatorLU wrote: ↑

Thu Apr 09, 2020 4:58 am

Source: Economist GMAT

A rocket is launched at 41,400 kilometers per hour. What is the speed of the rocket in meters per second?

A. 115
B. 1150
C. 11,500
D. 69,000
E. 149,040

The OA is C

We are given that the rate of the rocket is 41,400 kilometers per hour, or 41,400 km/1 hour, and we need to determine the speed in meters per second. Let’s first convert kilometers to meters.

Since 1 kilometer = 1,000 meters, then 41,400 km = 41,400 x 1,000 = 41,400,000 meters

We also know that 1 hour = 3,600 seconds.

So, our new rate is:

41,400,000 meters/3,600 seconds = 11,500 m/s

Answer: C