Question

Find the sum of all multiple of 3 natural number between 1 to 100

Answer 1

Answer:

Sn = 1683

Step-by-step explanation:

3 , 6 , 9 ....................... 99

a = 3

d = 6 - 3 = 3

an = 99

n = ??

Sn = ??

an = a + (n - 1) d

99 = 3 + (n - 1)3

99 = 3 + 3n - 3

3n = 99

n = 33

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

        2

Sn = 33 [2*3 + (33 - 1) 3]

        2

Sn = 16.5 [6 + 96]

Sn = 16.5 * 102

Sn = 1683

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