Shanti while driving her car at a speed of 68 km/h, observes that at some moment a moving bus is 40 m ahead of her car. After 10 sec she finds that she is 60 m ahead of the bus. What is the speed of the bus?

Correct option is B

Given:

Speed of Shanti = 68 km/hr

Distance Shanti is behind the bus = 40 m

Distance after 10 sec = 60 m

Formula Used:

Speed =$$\ \frac{Distance}{Time}$$​​

Distance = $$Speed \times Time$$​​

Solution:

Speed of Shanti in m/sec = $$68 \times\frac{5}{18} = \frac{170}{9}\ m/sec$$​​

Distance travelled in Shanti in 10 sec = $$10\times\frac{170}{9} = \frac{1700}{9} m$$​​

If Shanti was 40 m behind and 10 seconds later she was 60 m ahead of bus it means she travelled (40 + 60) m more than bus;

Distance travelled by bus = $$\frac{1700}{9} - 100 = \frac{1700-900}{9} =\frac{800}{9}\ m$$​​

Speed of bus =$$\frac{\frac{800}{9}}{10} = \frac{80}{9}m/sec$$​​

Speed of bus in km/hr = $$\frac{80}{9}m/sec\times\frac{18}{5}= 32\ km/hr$$​​