Latest Elitmus Aptitude Question SOLUTION: two friends suppose A and B run on circular track in clockwise and anti- clockwise direction respectively . A runs 1 km in 4 minutes. What should be the speed of B so that they mee

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two friends suppose A and B run on circular track in clockwise and anti- clockwise direction respectively . A runs 1 km in 4 minutes. What should be the speed of B so that they meet 24 times in 45 minutes.
1. 17 2. 18
other options I not remember.

Asked In Elitmus raksha singh (8 years ago)

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DEEPAK RAJ  (8 years ago)

You missed 1 thing. Length of the track was given. It was 1 KM. And the ques was that A runs 1 round in 4 minutes. Answer would be 17 KM/hr.

A runs 1 KM in 4 min. So, A's speed = 15 KM/hr.

Suppose, they meet in x hr. It means they will complete 1 round i.e. 1 km in x hr.

Let B's speed = y KM/hr.

then, 15x + yx = 1.
=> x(15+y) = 1
=> x = 1/(15+y)

So, to complete 1 round they take 1/(15+y) hr.

Now, according to ques they complete 24 round in 45 min. i.e. 3/4 hr.

So, 1(15+y)*24 = 3/4 .

Putting y = 17 KM/hr we will get our answer.

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pravendra yadav  (8 years ago)

one more approach:

by the concept of relative velocity..

A runs 1 KM in 4 min. So, A's speed = 15 KM/hr.

let speed of B=x

as B is moving in opposite direction, so by the concept of relativity we can assume,

speed of B=15+x
24th round takes 45 min(3/4 hr)
1 round will take 3/(24*4) hrs

therefore relative distance travelled by B=1km
relative speed of B * time taken to complete 1 round =1 km

i.e, (15+x)*3/(4*24)=1
15+x=32

hence x=17 km/hr

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Rajkumar saini  (8 years ago)

Data Inadequate....because we don't know about length of track..

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Md Mosaraf  (8 years ago)

Ans 18km/hr

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Ravi  (8 years ago)

Data Inadequate

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swati kisan jadhav  (8 years ago)

please explain how 18km/hr

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santosh  (8 years ago)

ans -17 check

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