Distance and Time Quiz Set 010

Question 1

A boy walks along the three edges of an equilateral triangle at average speeds of 7 km/h, 4 km/h and 5 km/h. What is the average speed along the whole journey?

A

\$5{5/83}\$ kmph.

B

\$6{11/82}\$ kmph.

C

\$3{82/85}\$ kmph.

D

\$7{74/85}\$ kmph.

Soln.
Ans: a

Let the edge of the triangle be L. Total distance travelled = 3L. Time taken = \$L/7 + L/4 + L/5\$. So overall average speed = \${3L}/{L/7 + L/4 + L/5}\$ which simplifies to \${420/83}\$, which is same as: \$5{5/83}\$ km/h.

Question 2

A car is moving at a speed of 90 kmph. What is the speed in m/s?

A

25 m/s.

B

26 m/s.

C

24 m/s.

D

27 m/s.

Soln.
Ans: a

We know 1kmph = \$5/18\$ m/s. So 90kmph = \$5/18 × 90\$ = 25 m/s.

Question 3

An aircraft was on a 220 km journey. Its engine developed a snag so it had to slow down. It's average speed reduced by 2km/h, as a result of which it reached its destination late by 1 hour. What was the actual duration of the journey?

A

10 hrs.

B

11 hrs.

C

9 hrs.

D

12 hrs.

Soln.
Ans: a

Let x be the actual duration of the journey. Then, \$220/x - 220/{x + 1} = 2\$. Which gives 220 × \$1/{x (x + 1)} = 2\$. Solving for x, or by trying the options one by one, we get x = 10 hours.

Question 4

A car is moving at a speed of 35 meters per second. What is the speed in Km/h?

A

126 kmph.

B

127 kmph.

C

125 kmph.

D

128 kmph.

Soln.
Ans: a

We know 1m/s = \$18/5\$ kmph. So 35m/s = \$18/5 × 35\$ = 126 kmph.

Question 5

A school bus covers a certain distance in 3 hours at a speed of 42 km/h. At what speed should it travel to cover the same distance in 6 hours?

A

21 kmph.

B

22 kmph.

C

20 kmph.

D

23 kmph.

Soln.
Ans: a

Let t1, v1 and t2, v2 be the speeds and times for covering the same distance. We have t1 × v1 = t2 × v2. From here we get v2 = \${3 × 42}/6\$ = 21km/h.