document.write( "Question 1209366: In an arithmetic sequence, the 23rd term is 2, and the 38th term is 3. What is the 41st term? \n" ); document.write( "
Algebra.Com's Answer #848683 by greenestamps(13200)\"\" \"About 
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\n" ); document.write( "First, informally -- which can be more educational than doing the formal mathematics....

\n" ); document.write( "The 38th term is 15 terms after the 23rd term, and the value of the 38th term is 1 more than the value of the 23rd term. So the common difference in the sequence is 1/15.

\n" ); document.write( "The 41st term is 3 terms after the 38th term, so the value of the 41st term is 3 times 1/15 greater than the 38th term. 3*(1/15) = 3/15 = 1/5 = 0.2; the 41st term is 3+0.2 = 3.2.

\n" ); document.write( "ANSWER: 3.2

\n" ); document.write( "Formally....

\n" ); document.write( "if a is the first term and d is the common difference, then...

\n" ); document.write( "23rd term is a+22d
\n" ); document.write( "38th term is a+37d

\n" ); document.write( "a+37d=3
\n" ); document.write( "a+22d=2

\n" ); document.write( "Subtract the second equation from the first

\n" ); document.write( "15d=1
\n" ); document.write( "d=1/15

\n" ); document.write( "a+22d=2
\n" ); document.write( "a+(22/15)=2=30/15
\n" ); document.write( "a=8/15

\n" ); document.write( "The first term is 8/15; the common difference is 1/15.

\n" ); document.write( "The 41st term is a+40d = 8/15+40/15 = 48/15 = 16/5 = 3.2

\n" ); document.write( "ANSWER (again): 3.2

\n" ); document.write( "Note that, if we use the standard formal textbook method for solving the problem, we have to do a lot more work (to find the first term of the sequence) than we did using an informal method.

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