Question

find out the sum of all natural numbers between 1 and 145 which are divisible by 4​

Answer 1

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$\underline{Step-by-step\: explanation:}$

Given: To find the sum of all natural numbers between 1 and 145 which are divisible by 4.

The number of natural numbers between 1 and 145 divisible by 4 are

 4, 8, 12, 16, 20....................144

a = 4, d = 4, n = ?,  an = 144

  an = a + (n - 1)d

    144    = 4 + (n - 1)4

   140 = 4n - 4

  4n = 144

 n = 36

Now to find sum we have

Sn = n / 2 [2 a + (n - 1)d]

Sn = 36 / 2 [2(4) + (36 - 1)4]

Sn = 18(8 + 140)

Sn = 18 x 148

Sn = 2664

The sum of natural numbers divisible by 4 between 1 and 145 is 2664.