If one small mole can dig a mole hole in nine hours, a medium mole can dig a mole hole in 6 hours and a large mole can dig a mole hole in four and a half hours. How long will it take one small, one medium and one large mole to dig a mole hole if they all work together?

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1 medium mole equivalent to 1.5 small moles

=> 1 small + 1 medium + 1 large equivalent to 4.5 small

=> it will take them 2 hours to complete a hole

You are correct, Roolstar!

Here’s another way to figure it:

2 hours.

The small mole can dig a mole hole in nine hours so digs 1/9 in one hour.

The medium mole can dig a mole hole in 6 hours so digs 1/6 in one hour.

The large mole can dig a mole hole in four and a half hours so digs 1/4.5 in one hour.

1/9 + 1/6 + 1/4.5 = 0.5. So in one hour, they have dug half a mole hole between them, the whole mole hole will therefore take 2 hours.

You are today’s winner.

I think trio will take 2 hours to dig a hole if they all worked together.

Check this brainteaser if you wish –

http://www.iqtestexperts.com/brainteasers/