There are 20 coins placed on a table such that tails is showing up. Suddenly electricity goes off and a boy sitting nearby inverts few coins and then he asks another boy to select some coins such that number of inverted coins is equal in every other subpart. He selects 8 coins and invert those 8 coins , and when electricity comes back he sees equal number of inverted coins in both subparts. Tell how many coins did first boy inverted.

P.S. The question is not original.

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TopNewestIf you assume n coins to be inverted in both, then first would have inverted his n and others 8-n. So he inverted 8 in total – Prince Loomba · 1 year, 2 months ago

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Its answer is 8 – Prince Loomba · 1 year, 2 months ago

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Sounds like a potentially good puzzler. Although, what a

subpartis, isn't clear. – Agnishom Chattopadhyay · 1 year, 2 months agoLog in to reply

– Ratul Pan · 1 year, 2 months ago

The problem is given in a technothlon problem . I am also confused with the term subparts. But it sounds like two groups from the phrase "equal number of inverted coins in both subparts". The options were given as 5 , 8 , 10 , 12. Now you can try.......Log in to reply

– Agnishom Chattopadhyay · 1 year, 2 months ago

What is a technothlon?Log in to reply

– Prince Loomba · 1 year, 2 months ago

From classes 9th to 12thLog in to reply

– Ratul Pan · 1 year, 2 months ago

It is an exam purely based on logic conducted by IIT Guwahati. You can check it out in the official website i.e. technothlon.techniche.orgLog in to reply

– Agnishom Chattopadhyay · 1 year, 2 months ago

Oh. Thanks for the linkLog in to reply

– Ratul Pan · 1 year, 2 months ago

Its my pleasure...... You can register now also. The exam is on 17 th of july and I think registrations are open till 13 th of july.....Log in to reply

Probably 10 – Hemanth K · 1 year, 2 months ago

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– Prince Loomba · 1 year, 2 months ago

Read my answer. Its 8Log in to reply