GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 06 Dec 2019, 16:36

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# M21-12

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 59587

### Show Tags

16 Sep 2014, 01:10
00:00

Difficulty:

15% (low)

Question Stats:

81% (01:37) correct 19% (01:42) wrong based on 148 sessions

### HideShow timer Statistics

If the diameter of each of a car's wheels is 0.4 meters, approximately, what was the average speed of the car for its three-hour trip in which each wheel made 100,000 revolutions?

A. 33 kmh
B. 35 kmh
C. 42 kmh
D. 47 kmh
E. 51 kmh

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 59587

### Show Tags

16 Sep 2014, 01:10
1
Official Solution:

If the diameter of each of a car's wheels is 0.4 meters, approximately, what was the average speed of the car for its three-hour trip in which each wheel made 100,000 revolutions?

A. 33 kmh
B. 35 kmh
C. 42 kmh
D. 47 kmh
E. 51 kmh

The circumference of the wheel is $$0.4\pi$$ or approximately 1.2 meters. The car went $$100,000*1.2$$ meters or $$100*1.2 = 120$$ km. Because we used 3 instead of 3.14, the actual average speed of the car must be somewhat higher than $$\frac{120}{3} = 40$$kmh. The best answer is C.

_________________
Intern
Joined: 28 May 2017
Posts: 7

### Show Tags

16 Oct 2018, 19:07
I feel this solution is wrong.

Total distance without rounding off = 40*3.414 km
Avg Speed = 40*3.414/3 = 45.52km/hr
None of the options has the answer.
In this case, Option D is the closest possible choice.
Math Expert
Joined: 02 Sep 2009
Posts: 59587

### Show Tags

16 Oct 2018, 20:53
sarvesh93sah wrote:
I feel this solution is wrong.

Total distance without rounding off = 40*3.414 km
Avg Speed = 40*3.414/3 = 45.52km/hr
None of the options has the answer.
In this case, Option D is the closest possible choice.

__________________________
$$\pi = 3.141...$$, not 3.414.
_________________
Intern
Joined: 28 May 2017
Posts: 7

### Show Tags

16 Oct 2018, 23:33
Bunuel wrote:
sarvesh93sah wrote:
I feel this solution is wrong.

Total distance without rounding off = 40*3.414 km
Avg Speed = 40*3.414/3 = 45.52km/hr
None of the options has the answer.
In this case, Option D is the closest possible choice.

__________________________
$$\pi = 3.141...$$, not 3.414.

Re: M21-12   [#permalink] 16 Oct 2018, 23:33
Display posts from previous: Sort by

# M21-12

Moderators: chetan2u, Bunuel