Question

find the sum of 15 terms of the AP 1/2,1/2,1/2,........

Answer 1

Hi Friend !!!

Here is ur answer !!!

a = 1/2

d = 1/2 - 1/2

= 0

n = 15

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

= 15/2 (2(1/2) + 14(0))

= 15/2 (1+0)

= 15/2 (1)

= 15/2


Hope it helps u :-)

Answer 2

Common difference = 1/2 - 1/2 = 0 
first term = 1/2 
Last term = 15th term = a + 14(d)
                                      = 1/2 + 14(0)
                                      = 1/2 + 0
                                      = 1/2 

=====================================

$S_{n} = \frac{n}{2} [First term + last term]$

Here,

$S_{15} = \frac{15}{2} [1/2 + 1/2]$

$S_{15} = \frac{15}{2}[1]$

Sum of 15 terms = 15/2 = 7.5 



i hope this will help you

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