Question 933569: we have to arrange chairs for the audience a in the first row we can place 20 chairs in the next 22 chairs 2 chairs can be added to each row than the previous one we have to arrange 50 so how many chairs are needed WE HAVE TO USE AP FORMULA
(arithmetic progression)
so how many chairs will be in the 25th row?
with thousand how many perfect rows can you make?
how many chairs will be in the last row?
what are the difference in the number of chairs for arranging 25 rows and 50 rows?
in which row 50 chairs will exist?
will you be able to make perfect rows with thousand chairs? if not how many chairs are needed to make the row perfect?
if you need to make 2 more rows how more chairs are needed?
Answer by MathLover1(20849)   (Show Source):
You can put this solution on YOUR website! # of chairs in rows: 20, 22,24,26,28,30,32,34,36,38,40,42,44,46,48,50
difference 
a.
how many chairs will be in the 25th row?
 ...chairs will be in the 25th row
b.
with  chairs how many perfect rows can you make
 .....# of rows you can make, since  is NOT a perfect number,
the only perfect numbers between  and are  ,  ,  ; since  , with chairs you can make only  perfect rows which are rows and
c.
how many chairs will be in the last row?
the last row is  :
 ...# chairs in the last row
d.
what are the difference in the number of chairs for arranging 25 rows and 50 rows?
...chairs will be in the 25th row
the difference in the number of chairs for arranging  rows and  rows is 
or, since the difference in the number of chairs for arranging between two rows is 2 chairs, then
between rows and will be 
e.
in which row chairs will exist?
 .....row in which chairs will exist
f.
will you be able to make perfect rows with thousand chairs? if not how many chairs are needed to make the row perfect?
from c. we know that
 and is not perfect row because is NOT a perfect number
first perfect number is  (see b.); so we need 5more rows or 10 more chairs
g.
if you need to add  more rows you will have  rows
as given,for each additional row you need more chair; so, to make more rows you will need  more chairs to row which is  ; so, we will have  chairs in row #
check:
 ...so, we got a row number
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