Solve these simple math questions to crack SI exam

Hyderabad: This article is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some questions and answers along with explanations 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 car reached Raipur from Somgarh in 35 minutes with an average speed of 69 km/hr. If the average speed is increased by 36 km/hr, how much time will it take to cover the same distance?

1) 24 minutes 2) 27 minutes 3) 23 minutes 4) 29 minutes

5) None of these

Ans: 3

Explanation

Speed = 69 km/hr

Time = 35 minutes = 35/60 hours
Distance = 35/60 × 69 km
Second case Speed = 69 36 = 105 km/hr
Second case time = 35/60 × 69 × 1/105 = 23/60 hrs = 23 minutes

3. 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
= 24km/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.

4. 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 2nd day
Let Distance = x km Distance = x km
Speed = 3 km/hr Speed = 4 km/hr
Time = x/3 hrs 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
5. 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

Banda Ravipal Reddy
Director, SIGMA

Sai Institute of General Mental Ability

Hyderabad