Question

7 + 15 + 23 + 31 +......+255 =?​

Answer 1

Answer:

Step-by-step explanation:

a=7

c.d.=8

$tx_{n}$=255

n=? and $S{n}$=?

$tx_{n}$=a+(n-1)d

255=7+(n-1)8

255-7=(n-1)8

248=(n-1)8

$\frac{248}{8}$=n-1

31=n-1

n=32

NOW   $S_{n}$=$\frac{n}{2}${2a+(n-1)d}

$S_{n}$=$\frac{32}{2}$[2×7+(32-1)8]

                       =16[14+31×8]

                        =16[14+241]

                        =16×255

                       =4080

So your anwer is 4080.

HOPE IT HELPS YOU

PLEASE MARKS AS A BRAINLIST.....

Answer 2

$\boxed{Explained\:Answer}$

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a=7

c.d.=8

a+(n-1)d

255=7+(n-1)8

255-7=(n-1)8

248=(n-1)8

=n-1

31=n-1

n=32

[2×7+(32-1)8]

                       =16[14+31×8]

                        =16[14+241]

                        =16×255

                       =4080

anwer is 4080.