Solve these questions to crack the SI exam

This article helps in the preparation for the Sub-Inspector of Police recruitment exam. Here are some questions and answers on the Time and Distance topic.

1. A car travels a distance of 45 km at the speed of 15 km/hr. It covers the next 50 km of its journey at the speed of 25 km/hr and the last 25 km of its journey at the speed of 10 km/hr. What is the average speed of the car?
1) 40 km/hr 2) 24 km/hr
3) 15 km/hr 4) 18 km/hr
5) None of these
Ans: 5

Explanation
Time for first 45 km
= 45/15 = 3 hrs
Time for next 50 km = 50/25 = 2 hrs
Time for last 25 km = 25/10 = 2.5 hrs
The average speed =
Total distance / Total Time
45+50+25/ 3 +2+2.5 = 120/7.5 = 16 km/hr

2. A person travelled from his house to office at 15 km/hr and office to house at 60 km/hr. The time for total journey is 30 minutes. Then find the distance between house and office.
1) 6 km 2) 12 km 3) 18 km
4) 24 km 5) None of these
Ans: 1

Explanation
His average speed = 2×15×60/ 15+60
= 2×15×60/ 75
= 24 km/hr
Time = 30 minutes = ½ hr
Total distance (house to office and office to house) = ½ × 24 = 12 km
The distance between house and office = 12/2 = 6 km.
3. A person travelled from house to office at 3 km/hr and reached his office 9 minutes late. Next day, he travelled from house to office at 4 km/hr and reached 6 minutes early. Find the distance between house and office?
1) 3 km 2) 5 km 3) 4 km 4) 6 km
Ans: 1

Explanation
1st day
Let Distance = x km
Speed = 3 km/hr
Time = x/3 hrs

2nd day
Distance = x km
Speed = 4 km/hr
Time = x/4 hrs
The time difference in 2 days = 9+6 = 15 minutes = 15/60 hrs = 1/4 hrs
According to the question
x/3 – x/4 = 1/4
4x – 3x = 3
x = 3 km
The distance between house and
office = 3 km

4. Ramesh sets out to cycle from A to B and at the same time Suresh starts from B to A. After passing each other, they complete their journey in 9 hours and 16 hours respectively. At what speed does Suresh cycle if Ramesh cycles at 16 km/hr?
1) 12 km/hr 2) 16 km/hr
3) 14 km/hr 4) Can’t be determined 5) None of these
Ans: 1

Explanation
Ramesh’s Speed: Suresh’s Speed
= √16:√9 = 4:3
Suresh’s Speed =3/4 × 16 =12 km/hr