ObservANT Bros!

Logic Level 1

Anna and Thamma stand at each end of a straight line segment. Anna sends 30 ants towards Thamma, one after another. Thamma sends 60 ants towards Anna. All ants travel along the straight line segment. Whenever two ants collide, they simply bounce back and start travelling in the opposite direction.

How many ants reach Thamma?


The answer is 30.

Ayush G Rai by Ayush G Rai , 20, India

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3 solutions

Abc Xyz
May 4, 2016

Clearly the 30 ants of Anna will collide with the first 30 ants of Thamma.

Therefore those 30 ants will start moving towards where they came from.

Also the next 30 ants of Thamma will go towards Anna .

Therefore total ants which reach Anna are 60.

Therefore total ants which reach Thamma are 30 \boxed{30}

* The best way to solve this question is to visualise this question.

2 Helpful 0 Interesting 0 Brilliant 0 Confused

Good solution!!!

Ayush G Rai - 5 years, 1 month ago

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Thanks !!!

abc xyz - 5 years, 1 month ago
Tran Hieu
May 6, 2016

Because we only count the number of ants, we can consider they are the same. When two ants collide, they bounce back, but because they are the same we can consider they "walk through" each other, so that leads to the result

1 Helpful 0 Interesting 0 Brilliant 0 Confused

Good solution!!

Ayush G Rai - 5 years, 1 month ago
Finn C
May 20, 2016

I don't understand how only 33% of people got it right! Its fairly straightforward... :)

0 Helpful 0 Interesting 0 Brilliant 0 Confused

I think you did not understand my question correctly.

Ayush G Rai - 5 years ago

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