CoCubes Speed & Distance Question and Answers Quiz-1

Let the man from Delhi be A and that from Rohtak be B.

After passing each other A takes 10/3 hrs to reach Rohtak.

The speed of 8kmph.

The distance from their meeting point to rohtak is :

10/3 × 8 = 80/3 km

Let the total distance be x.

The distance traveled by B to Delhi is :

= (X - 80/3) km

Time = 16/3 hrs

They took the same time to meet A having traveled (x - 80/3)km and B having traveled 80/3 km

Let speed of B be y

(X - 80/3)/8 = (80/3) / y

Xy - 80/3y = 640/3

y (x - 80/3) = 640/3

Y = (640/3) / (x - 80/3)

The second face of the journey :

A takes = (80/3) /8 hrs

B takes = (x - 80/3) / y = 16/3

= 3x - 80 = 16y

Substituting the value of y in this we have :

3x - 80 = 16{(640/3)/(x - 80/3)

(3x - 80)(x - 80/3) = 10240/3

3x² - 80x - 80x + 6400/3 = 10240/3

3x² - 160x + 6400/3 = 10240/3

3x² - 160x - 3840/3 = 0

3x² - 160x - 1280 = 0

We solve for x using quadratic formula :

{160 +/- √(160² + 4 × 3 × 1280)} /2 × 3

{160 +/- 202.39} /6

x = 60.40 km

Lets substitute this value in the following equation :
3x - 80 = 16y

We have :

3 × 60.4 - 80 = 16y

101.2 = 16y

Y = 101.2/16
= 6.325 km/h

As a work is done by 28 men in 15 days at the rate of 6hr per day
or, 28 men take 15×6 hr to finish the work.
or, 28 men take 90 hr to finish the work.
or, 1 man will take 90×28 hr to finish 1 work.
or, amount of work done by 1 man in 1 hr = 1/2520 work

no. of days =2520/21×8=2520/168= 15 days.

Correct Answer : D

Explanation:

Speed = distance/time

Distance= speed * time = (60-45) * 48 * ( 5/18)

( relative speed in same direction is s1-s2 and kmph to m/sec 5/18) = 200m

Length of the Train = 240 m.

Time taken by it to cross the Pole = 15 seconds.

∵ Speed = Distance or length of the train/Time

∴ Speed = 240/15

⇒ Speed of the train = 16 m/s.

Hence, the speed of the train is 16 m/s.

Let length of platform = P m
we know,
distance = speed × time
here,
time = 1.5 × 60 sec = 90 sec
speed = 54 × 5/18 = 15 m/s
distance = (1200 + P) m

1200 + P = 15 × 90
1200 + P = 1350
P = 150 m

hence, Length of platform = 150 m

Since they are having same length, let. It be x.

Now, speed of Ist train=x/4.

Speed of 2nd train=x/5.

As per question, when moving in opposite direction, total length=x+x= 2x.

relative speed= (x/4)+(x/5)=(9x/20).

Time taken=(2x)÷(9x/20)=40/9=4.44 second

Correct Answer : A

Correct Answer : C

Explanation:

With 60 kmph in 3 hours train ‘A’ covers 180 kms. Train B speed is 12kmph more than train ‘A’. Because train B started 3 hours later so it has to cover 180 extra with extra 12kmph speed. Time taken is = 180/12 = 15 hours So 15 hours from 2p.m is 5a.m on the next day