A Man travelled a distance of 61 km in 9 hours. He travelled partly on foot at 4 km/hr and partly on bicycle at 9 km/hr. What is the distance travelled on foot?

Answer: Option D

Explanation:

We need to get the answer in meters. So we will first of change distance from km/hour to meter/sec by multiplying it with 5/18 and also change 15 minutes to seconds by multiplying it with 60.

$$\begin{aligned} Speed = 5* \frac{5}{18} = \frac{25}{18}m/sec \\ Time = 15*60 seconds = 900 seconds \\ Distance = Time * Speed \\ Distance = \frac{25}{18}*900 = 1250 meter \end{aligned}$$

Answer: Option B

Explanation:

We are having time and speed given, so first we will calculate the distance. Then we can get new speed for given time and distance.
Lets solve it.

Time = 50/60 hr = 5/6 hr
Speed = 48 mph
Distance = S*T = 48 * 5/6 = 40 km

New time will be 40 minutes so,
Time = 40/60 hr = 2/3 hr
Now we know,
Speed = Distance/Time
New speed = 40*3/2 kmph = 60kmph

Answer: Option C

Explanation:

In this type of questions we need to get the relative speed between them,
The relative speed of the boys = 5.5kmph – 5kmph
= 0.5 kmph

Distance between them is 8.5 km
Time = Distance/Speed
Time= 8.5km / 0.5 kmph = 17 hrs

Answer: Option C

Explanation:

$$\begin{aligned} Speed = \frac{Distance}{Time} \\ Distance = 750 meter \\ Time = \text{2 min 30 sec} = 150 sec \\ Speed = \frac{750}{150} = 5 m/sec \\ => 5*\frac{18}{5} km/hr = 18 km/hr \end{aligned}$$

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