document.write( "Question 1166951: For the arithmetic sequence with t7 = 0.6 and t12 = -0.4, find t20. \n" ); document.write( "

Algebra.Com's Answer #791507 by ikleyn(52790) $\"\"$ $\"About$

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\n" ); document.write( "For the arithmetic sequence with t7 = 0.6 and t12 = -0.4, find t20.
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document.write( "The distance between 0.6 and -0.4 in number line is 1 unit (0.6 - (-0.4) = 1).\r\n" );
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document.write( "There are 5 equal gaps between these points in number line, representing common difference of the arithmetic progression.\r\n" );
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document.write( "Hence, each gap has the length  1/5 = 0.2.\r\n" );
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document.write( "It means that the common difference of the AP is -0.2.   (It is negative, since the progression decreases).\r\n" );
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document.write( "Next, from    to  ,  there are 8 gaps in the number line, so the 20-th term is\r\n" );
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document.write( "     =  + 8*d = -0.4 + 8*(-0.2) = -0.4 - 1.6 = -2.0.    ANSWER\r\n" );
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