Question

find the sum of first 123 even natural numbers​

Answer 1

Step-by-step explanation:

15,252 is the right answer for your question

Answer 2

$\mathtt \red {We \: know \: that , }$

$\mathtt \red {The \: even \: natural \: numbers \: are \: 2 ,4 , 6 , 8 \: . . . }$

$\mathtt \red {First \: term \: (a) =2}$

$\mathtt \red {D \: = \: n_{2}- \: n_{1}}$

$\mathtt \red {D \: = \: 4 \: - \: 2 \: = \: 2}$

$\mathtt \red {N \: = \: 123}$

$\mathtt \red {S_{n}\: \: \: \: = \: \: \frac{n}{2}[2a + (n - 1)d]}$

$\mathtt \red {S_{123} \: = \: \frac{123}{2}[2(2) + (123 - 1)2]}$

$\mathtt \red {S_{123} \: = \: \frac{123}{2}[4 + (122)2]}$

$\mathtt \red {S_{123} \: = \: \frac{123}{2}[4 + (244)}$

$\mathtt \red {S_{123} \: = \: \frac{123}{2} \times 248}$

$\mathtt \red {S_{123} \: = \: {123} \times 124}$

$\boxed {\mathtt\red {S_{123} \: = \: 15252}}$