document.write( "Question 176989This question is from textbook Mathmatics for Elementary Teachers
\n" ); document.write( ": An auditorium has 50 rows of seats. The first row has 20 seats, the second has 21, each row having 1 more seat than the previous. How many seats are there together?\r
\n" ); document.write( "\n" ); document.write( "(I figured it out by multiplying 50x20, and then adding the product with the sum of 49+48..., but I do not know a short cut or formula to get the answer) \n" ); document.write( "
Algebra.Com's Answer #132039 by solver91311(24713)\"\" \"About 
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There are 20 seats in the first row and 20 + 50 - 1 = 69 seats in the last row. You need the sum of the integers from 20 to 69 inclusive.\r
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\n" ); document.write( "\n" ); document.write( "20 plus 69 = 89\r
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\n" ); document.write( "\n" ); document.write( "21 plus 68 = 89\r
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\n" ); document.write( "\n" ); document.write( "and so on\r
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\n" ); document.write( "\n" ); document.write( "You have 25 (50 divided by 2) such pairs that add to 89, so 25 X 89 = 2225\r
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\n" ); document.write( "\n" ); document.write( "In general, the sum of a series of integers is \"%28%28a+%2B+l%29n%29%2F2\" where a is the first integer, l is the last integer, and n is the number of integers.\r
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