Question

After nearly 5-6 km, Jack could now see the city vaguely. He was so particular about time that he used to note down the distance and the time he took to go to office every day. He had a picture of one of those notes on his tablet. Now using the data from the picture, find out how many minutes will Jack roughly take to reach Cottage city if it is still 4 km away?

• A. Nearly 45 minutes
• B. Nearly 50 minutes
• C. Nearly 55 minutes
• D. Nearly 60 minutes

Answer 1

The correct option is C

Nearly 55 minutes

Speed is generally given in km/hr e.g., 50 km/hr, which can also be represented as $\frac{50km}{1hr}$

We can derive an equation for the speed as

Speed =$\frac{Distance}{Time}$

$\begin{array}{cccc}Day& Distance& Time& Speed=\frac{Distance}{Time}\\ Monday& 2km& 0.5hr& \frac{2km}{0.5hr}=4km/hr\\ Tuesday& 2km& 0.4hr& \frac{2km}{0.4hr}=5km/hr\\ Wednesday& 2km& 0.5hr& \frac{2km}{0.5hr}=4km/hr\end{array}$

Average Speed = $\frac{\text{4 km/hr + 5 km/hr + 4 km/hr}}{3}$ = $\frac{13}{3}$ km/hr = $\frac{52}{12}$ km/hr = 4.33 km/hr
So, time taken to travel 4 km more = $\frac{4}{4.33}\times 60=$ 55 minutes (approximately)