Answers

2016-01-20T22:13:19+05:30
20. If one plank of wood slows it by 1/20 then 20 of them would reduce it to zero thus stopping it completely
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2016-01-21T22:57:52+05:30
After passing the 20th plank the velocity of the bullet will become zero so 20 planks is the answer.
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