May 2016

Killer cats!

Cats at play

I was munching some snacks; three cats appeared from nowhere and began a meowing contest begging for their share. Downright annoying!

Just then my friend Alok arrived. Looking first at the cats and then at me he asked, "If three cats can catch three mice in three minutes, how many cats will be needed to catch one hundred mice in 100 minutes?"

This was all the more annoying; first the cats and then Alok with his riddles!

"Hey if you answer correctly, I will treat you to a mouse, er .... a hot dog I mean," he said.

That made me sit up and take notice. At school we had solved questions of a similar kind: "If ten people can complete a piece of work in 20 days, then how many people will be required to, etc, etc." So I was sure I could solve it.

I brought out my notebook, a pencil, an eraser, and a ruler (this was to underline my answer), and set to work. Even after an hour's hard labour, I was nowhere near discovering how many cats would be required to catch 100 mice in 100 minutes. The only progress I had made was in establishing that one cat could catch 33.333333..... mice in 100 minutes. Now, if that figure had been 33, I would have been happy; if it had been 34, I would have patted the cat. But 33.333333.......! How can there be 33.333333.... mice? The three cats, meanwhile, finding that I had put aside my snacks had stolen from the plate and were quietly enjoying a meal. I flung the notebook at the first cat, the eraser at the second cat, and the pencil at the third cat.

I gave up. "I give up," I told Alok. But I begged him to tell me the answer. He told me, and I flung the ruler at him. Will you help me find the answer? I think Alok was pulling my leg. I will repeat the question: If three cats can catch three mice in three minutes, how many cats will be needed to catch one hundred mice in 100 minutes?

Click here for the solution

Some useful links for
your career:

  • Union Public Service Commission -
  • IIT-Kharagpur -
  • Indian Statistical Institute -
  • Indian Institute of Technology Madras -
  • Indian Institute of Management, Ahmedabad -
  • Indian Institute of Mass Commission -
  • IIT Bombay -
  • Indian School of Mines, Dhanbad -
  • Birla Institute of Technology, Ranchi -
  • Central Institute of Fisheries Nautical and Engineering Training -
  • Indian Institute of Information Technology, Allahabad (Deemed University) -
  • Central Marine Fisheries Research Institute, Kochi -
  • Tata Institute of Social Sciences, Mumbai -

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