document.write( "Question 118654: What term in the sequence (1.6,1.2,0.8,0.4,...) is -38.4 ? I guessed 99 but was marked wrong . I don't know how to do this , please help me :) \n" ); document.write( "

Algebra.Com's Answer #86780 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
Look at the terms and see if you can determine the pattern.
\n" ); document.write( "First term = 1.6
\n" ); document.write( "Second term = 1.6-0.4 = 1.2
\n" ); document.write( "Third term = 1.6-0.4-0.4 = 0.8
\n" ); document.write( "Fourth term = 1.6-0.4-0.4-0.4 = 0.4
\n" ); document.write( "I think you can see the pattern.
\n" ); document.write( "Nth term = 1.6 - 0.4*(N-1)
\n" ); document.write( "Now that you have the formula, set it equal to the number to find N.
\n" ); document.write( " $\"1.6-0.4%2A%28N-1%29=-38.4\"$
\n" ); document.write( " $\"-0.4%2A%28N-1%29=-40.0\"$ Subtract 1.6 from both sides of the equation.
\n" ); document.write( " $\"N-1=100\"$ Divide both sides by 0.4.
\n" ); document.write( " $\"N=101\"$
\n" ); document.write( "Check your answer with your original formula.
\n" ); document.write( "101st term = 1.6 - 0.4(101-1)=1.6-40.0=-38.4.
\n" ); document.write( "The answer checks out. \n" ); document.write( "

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