If on each step, of a flight of 100 steps, there were birds equaling that of the step number, eg. on the First step there was one bird, on the Second there were two, on the Third there were three, and so on. How many birds would there be in total?
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n * (n + 1) / 2
n = 100
100 * (100 + 1) / 2 =>
50 * 101 =>
5050
n = 100
100 * (100 + 1) / 2 =>
50 * 101 =>
5050