Question

Mr. Ghosh Babu leaves his house daily at a particular time to go to his office. He reaches office 10minutes late when he travels at 20 kmph and 5 minutes early when he travels at 30 kmph. At what speed should he travel to reach office on time?

Answer 1

Let the distance between his house & office = d km
If his speed is 20 kmph time taken $=\frac{d}{20}hrs$
$=\frac{d}{20}\times 60minus=3dminuts$
30 kmph time taken $=\frac{d}{30}\times 60=2dminuts$
Correct time to reach office = 3d - 10 = 2d + 5 = t
d = 15 km
$\therefore$ The correct speed $=\frac{d}{t}=\frac{15}{35}km/min=\frac{\text{/}{15}^3}{\text{/}{35}^7}\times 60km/hr=\frac{180}{7}=25.71km/hr$