1.

Find the sum of 6 + 8 + 10 + 12 + 14 __________ + 40.1. 4242. 4003. 16004. 414

Answer» Correct Answer - Option 4 : 414

Given :

6 + 8 + 10 +12 + 14 .........       + 40 

Formula used :

Sum of first n even natural numbers = n (n + 1)

Calculations :

Add and subtract 6 in the series

6 + 6 + 8 + 10 + 12 + 14 .................. + 40 - 6 

2 + 4 + 6 + 8 + 10 + 12 ...................+ 40 - 6     (6 = 2 + 4)

Total number of terms from 2 to 40

n = (40 - 2)/2 + (1) = 20 (n is the total number of term, 40 is the last term and 2 is the common difference in the series)

Total number of terms(n) = 20

So,

2 + 4 + 6 + 8 + 10 ...................... 40 = 20 (20 + 1) 

⇒ 420 

2 + 4 + 6 + 8 + 10..................+ 40 - 6 = 420 - 6 

⇒ 414 

∴ The sum of the series will be 414 



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