Question 353260: how can i figure this math problem out classroom on one side of the drama building are all numbered with consecutive odd integers. If the first room on this side of the building is numbered d, write an expression in d for the sum of the first seven classroom numbered in a row. then simpilfy this expression.
i dont understand how to do it may u PLEASE explain to me
Answer by sudhanshu_kmr(1152)   (Show Source):
You can put this solution on YOUR website! First room is numbered with d then numbers are: d , (d+2),(d+4),.....
( to find next odd integer we add 2 , for example 3+2 = 5, 5 + 2 = 7 )
this is a series of arithmetic progression, where first term is d and
common difference is 2 ....
now we have to find the sum of first seven terms
to find sum of first n terms, we use Sn = ( n/2 ) * { 2a + (n-1)d }
where n : no. of terms
a : the first term
d : the common difference
here n = 7, a = d (according to question) , d = 2
S7= (7/2) * { 2d + (7-1)*2}
= (7/2) * { 2d + 12 }
= (7/2) * 2 { d + 6}
= 7{d + 6}
= 7d + 42
sum = 7d + 42
Sometimes there may be typing mistake in solution of a problem, so please ignore it. Understand the concept and try the problem yourself. If there is problem related to concept, contact at sudhanshu.cochin@gmail.com
Best of luck.......
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