Aptitude - Time and Distance - Discussion

Discussion Forum : Time and Distance - General Questions (Q.No. 2)
2.
An aeroplane covers a certain distance at a speed of 240 kmph in 5 hours. To cover the same distance in 1 hours, it must travel at a speed of:
300 kmph
360 kmph
600 kmph
720 kmph
Answer: Option
Explanation:

Distance = (240 x 5) = 1200 km.

Speed = Distance/Time

Speed = 1200/(5/3) km/hr.     [We can write 1 hours as 5/3 hours]

Required speed = 1200 x 3 km/hr = 720 km/hr.
5

Discussion:
146 comments Page 1 of 15.

Sreenath said:   1 decade ago
Hi, we know that speed=distance/time

Here distance is constant for different times
so speed o< 1/time
i.e
s1/s2=t2/t1

=> s2=s1*(t1/t2)

=> s2=240*[5/(5/3)]

=> s2=240*3

=> s2=720
here s2 is the speed when time is 5/3
remember when distance is constant speed o< 1/time
if speed constant time o< distance
if time is constant speed o< distance

Thanks.

Avinash said:   1 decade ago
Ramkumar,nothng hard in tat.first knw formula
distance=speed*time
speed=distance/time
time=speed/distance

now read the question.they given aeroplance covers distance of 240 km/hr in 5 hours so we need the total distance of 5 hours...
distance=speed*time
so distance=240*5=1200km
now we have to speed cover in 1+2/3 hours=5/3 hours
speed=distance/time
speed=(1200/5/3)kmph=(1200*3/5)kmph=720 kmph
(2)

Naren said:   9 years ago
Here they wrote fraction 5/3 as mixed numbers (1 2/3).

Let me explain how to write it.

Here, the whole number is 1.

The denominator is 3 and the numerator is 2.

I) 1st Multiply the whole number by the denominator. i.e. 3*1=3.

II) Add the result to the numerator: i.e 3+2=5.

III) Now The numerator is 5. The denominator remains 3. --> so 5/3.

We got the output.
(4)

Dayakar jitti said:   1 month ago
The given distance is =1200km.
speed =distance/time.

To cover the same is distance in 1^2/3 hours
which means we can write 1 power 2/3 as 1+2/3 therefore convert into fractions as,
1^2/3 = 1 + 2/3 = 3 * 1 + 2/3 which is 5/3 right so
according to the given problem we have to calculate the required speed.
Then speed =(1200 x 3/5)km/hr = 720 km/hr.
(3)

Sheela m b said:   1 decade ago
observe the formula carefully.
Distance = (240 x 5) = 1200 km.

Speed = Distance/Time
it says speed equals distance travelled by time taken and hence,
Speed = 1200/(5/3) km/hr.
since time is 5/3, the denominator(here it is 3) of denominator(the whole 5/3)becomes numerator. Therefore the following.
Required speed = 1200 x 3 km/hr = 720 km/hr.

RAPTOR said:   9 years ago
In the question I read it as to find the speed to cover the same distance in 1 hour (not as 1 2/3).

Either I read is right or all others read it wrong, I got the answer 1200kmph.

My logic is, since the total distance calculated is 1200 km, and in one hour it should cover the same distance, my answer is right.

Vaidik said:   3 years ago
According to the tri-rashi method.

5hours ----------->240km/h.
5/3hours ---------> (?).

5 x 240/5 x3 =80kmph.

I know this is wrong but speed should increase here because time is decreasing but I want to know why this method is not applicable here. Please can anyone help me to solve this?
(2)

Jabi Mir said:   10 years ago
Here, V1 = 240 km/h, T1 = 5 h, Also, V2= ?, T2 = 5/3.

We Know, V=S/T or S = VxT, But here distance is same,
Therefore, V1xT1=V2xT2, rearranging we get, V2 = V1xT1/T2.

Substituting values,
V2 = 240 x 5 / 5/3 or we can write it, V2 = 240 x 5 x 3/5.

On simplifying we get, V2=720 Km/h.
(1)

Prabakaran said:   6 years ago
On the first, the trail the aeroplane cross the distance in 5 hours at the speed of 240 km/hr.

For the same distance in 1(2/3) hours to resolve this cross multiplication (3*1*2-3= 3 hr).
So we have to multiply 240*3 to get the value of second trail speed is 720 km/hr.

Deepak said:   8 years ago
Distance = 240, 5 hour.

To cover same distance = x, 5/3 hour.

1 hour = 60 minutes, 5 hour = 300 minutes, 5/3 hour = 100 minutes.

= (5/3*60 minutes = 100 minutes).

= 240*300 = x*100.

72000 = x*100.

x = 72000/100.

x = 720.

So speed is 720 kmph.


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