The Busy Life of a Bird
There are
birds in a bush. One flies in for shelter from the wind, and three more fly out in fear. Those three come back with one more bird in their company, and two fly out to get some food.
, the number of remaining birds, is five.
What is ?
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1 solution
There are a few different ways to approach this problem, but the easiest way is the following:
There are two rounds in which the number of birds is changed. In round one, 1 bird is added and 3 are subtracted. In the second round, 4 birds are added and 2 are subtracted. We are then told that the total of remaining birds is 5 .
If we added the two from round 2 back and subtracted the four from the same round, we would get a total of 3 birds as of round 1. If we added the three subtracted birds from round 1 and subtracted the singular added bird, the total of birds at the start, or b , would equal 5 .
Since a and b are both equal to 5, a − b = 0 .