This question was previously asked in

DSSSB PRT General Section Official Paper - 13 Nov 2019 Shift 3

Option 4 : 7:00 p.m

Given:

A and B are at a distance of 400 km from each other at 5:00 AM.

Formula used:

Speed = Distance/Time

Distance = Speed × Time

Calculation:

According to the question,

Total distance of A and B = 400 km

Then, total distance of (5 : 00 to 9: 00) in 4 hours = 25 × 4 = 100 km

Relative speed of both people = 25 + 5 = 30 km/hr

Time will they meet on the next day = 300/30 = 10 hours

∴ Required time = 9 : 00 am + 10 hours = 7 : 00 PM .

__Additional Information__

Distance covered = Speed × Time

- Units of Time, Speed and Distance
- The basic unit of time is a second, which could also be expressed in other units such as minutes (min) and hours (hr).
- The basic unit of speed is meter per second m/s, which could also be expressed in other units such as m/min or km/h.
- The basic unit of distance meter (m), which could also be expressed in other units such as kilometre (km).
- To convert a speed given in m/s into a speed in km/h, multiply with 18/5.
- To convert a speed given in km/h into a speed in m/s, multiply with 5/18.
- 1 km = 1000 m
- 1 min = 60 sec.

Average speed:

- 1. When a body travels different distances at different speeds, the average speed is the amount of time taken to travel the total distance in total time, Therefore, the formula for Time Speed Distance is:
- Average speed = Total distance/ Total time
- 2. When the body travels at speeds of u and v units for equal distances:
- Average speed = 2uv/(u + v)

Relative speed:

- Consider two bodies moving at speeds u and v.
- 1. When they are moving in the same direction, the relative speed between the two bodies is the difference of their speeds,
- (u – v) if u > v
- (v – u) if v > u.
- 2. When they are moving in the opposite directions, the relative speed between the two bodies is the sum of their speeds,
- (u + v).