A car moves at 80 km/hr. What is the speed of the car in meters per second ?

Answer: Option C

Explanation:

Speed while going = 40 km/hr
Speed while returning = 150% of 40 = 60 km/hr

Average speed =

$$\begin{aligned} \frac{2xy}{x+y} \\ = \frac{2*40*60}{40+60} = \frac{4800}{100} \\ = 48 Km/hr \end{aligned}$$

Answer: Option A

Explanation:

Let the distance be 3x km,
then,

$$\begin{aligned} \frac{x}{3} +\frac{x}{4} +\frac{x}{5} = \frac{47}{60} \\ \frac{47x}{60} =\frac{47}{60} \\ x = 1 \end{aligned}$$
So total distance = 3*1 = 3 Km

Answer: Option D

Explanation:

Number of gaps between 41 poles = 40
So total distance between 41 poles = 40*50
= 2000 meter = 2 km
In 1 minute train is moving 2 km/minute.
Speed in hour = 2*60 = 120 km/hour

Answer: Option C

Explanation:

Relative speed between two = 6-1 = 5 round per hour

They will cross when one round will complete with relative speed,
which is 1/5 hour = 12 mins.

So 7:30 + 12 mins = 7:42

Answer: Option D

Explanation:

We need to calculate the distance, then we can calculate the time and finally our answer.
Lets solve this,

Let the distance travelled by x km
Time = Distance/Speed

$$\begin{aligned} \frac{x}{10} - \frac{x}{15} = 2 \\ \text{[because, 2 pm - 12 noon = 2 hours]} \\ 3x - 2x = 60 \\ x = 60. Time = \frac{Distance}{Speed} \\ Time @ 10km/hr = \frac{60}{10} = 6 hours \end{aligned}$$
So 2 P.M. - 6 = 8 A.M
Robert starts at 8 A.M.

He have to reach at 1 P.M. i.e, in 5 hours

So, Speed = 60/5 = 12 km/hr