Question

find the sum of first 123 even natural numbers

Answer 1

Construct an A.P,$2,4,6,8.....246\\a=2\\d=2\\n=123\\S_{123}=\frac{n}{2}[2a+(n-1)d]\\=\frac{123}{2}[2\cdot2+(123-1)2]\\=\frac{123}{2}[248]\\=123\cdot124\\=15252$

Answer 2

Answer:

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