Answer required in Km/Hr

Distance = 2400 Meters = \(\frac{2400}{1000}\) Kms = 2.4 Kilometers

Time = 1 Minute 48 Seconds = 60+48 = 108 seconds = \(\frac{108}{60}\) Minutes = \(\frac{108}{60*60}\) Hours

Speed \(= \frac{2.4}{\frac{108}{60*60}} = 0.8 * 10 * 10 = 80\)

Answer = 80

Kindly post all 5 options for this problem

Thanks

Hello alexa,

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1 Hour = 60 Minutes = 60*60 Seconds = 3600 seconds

We require to convert 108 seconds into hours

\(= \frac{108}{3600} Hours\)

\(Speed = \frac{distance}{time} = 2.4 * \frac{3600}{108} = 80\)

I arrived to the correct answer (80), but it took me quite long.

I have trouble converting units.

I did 1hr = 60min, and 60 min = 60 sec per min. So, 60x60 = 3,600 seconds in 1 hour.

So 108 seconds / 3,600 to convert to hours (this is the messy part, as then I divided 108/3,600 to get 0.031 hours).

Finally did 2.4 / 0.031 as 240 / 3 to get 80.

Any tips so that I can convert units and make the process easier and less prone to mistakes?

Thanks!

Distance= 2.4 Kms
Time= 1 + 48/60= 1.8/60 hrs

Speed= 2.4 * 60/1.8= 80 km/h
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Where are the options for this question.
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\(Speed = \frac{Distance}{Time}\)

We need to find Speed in \(km/hr\), hence convert the units of distance and time in \(kms\) and \(hrs\) respectively.

Given; Distance \(= 2400\) meters \(= 2.4\) kms

Time \(= 1\) minute \(48\) seconds \(= 60 + 48 = 108\) seconds \(= \frac{108}{3600}\) hrs \(= \frac{3}{100}\) hrs

Speed \(= \frac{2.4}{(3/100)} = \frac{2.4*100}{3}\)

Speed \(= \frac{240}{3} = 80\) km/hr

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Please Press "+1 Kudos" to appreciate.

Whenever, we need to convert a speed in km/hr to m/s, you multiply it by a factor of \(\frac{5}{18}\)
We arrive to \(\frac{5}{18}\) as follows :

1 km is 1000 meters
1 hr is 60 minute, and 1 minute is 60 seconds.
1 hr is 3600 seconds

So 1 km/hr essentially converts to \(\frac{1000}{3600}\) or \(\frac{5}{18}\)m/s
Therefore, In order to convert the speed from m/s to km/hr, you must multiply it by a factor of \(\frac{18}{5}\)

Coming back to the question in hand
The car travels 2400 meters in 1 minute 48 seconds(108 seconds)
Speed(in m/s) = \(\frac{Distance}{Time} = \frac{2400}{108} = \frac{200}{9}\)

In order to convert the speed in the format that it has been asked in, we multiply it by a factor of \(\frac{18}{5}\)

So, the converted speed(in km/hour as asked in the question) is \(\frac{200}{9}*\frac{18}{5}\) = 80 km/hr.

Hi Bunuel,
Can you please add options to this question to make it more GMAT-like!
Thanks
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If pressed for time, we can estimate:
1min 48s ≈ 2 min
2400/1000 = 2.4 km
1 hr = 60 min --> 60/2 = 30 * 2.4 km = 60+12 = 72 km/hr
Actual km/hr is a bit higher since we rounded up, choose C.

multiply with 18/5 to convert m/s to km/hr

1.48 seconds = 60+48 = 108 seconds

(2400/108)* 18/5 = 80

Option C is the answer

Bunuel I did something similar. Is this the correct way?

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