just an easy one

Algebra Level 1

In an arithmetic progression 1 , 6 , 11 , 16 … 1, 6, 11, 16 \ldots , find the 1000th term.

40000 4999 4996 4997

John Dave Berdon by John Dave Berdon , 23, Philippines

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1 solution

John Dave Berdon
Apr 29, 2014

in solving this you can use the standard formula an=a1+(n-1)d where a;1st term n;number of terms and d; is the common difference so from the problem shown our a1=1 n=1000 d=5 by substituting the values we can get the value of 4996.

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Or we can just observe the sequence. Each terms in the arithmetic sequence end with 1 and 6, alternately. Observe also that if the nth term is odd, then the last digit of that term is 1. And if the nth term is even, then the last digit of that term is 6. There is only one choice that has 6 in the last digit. So I q u i c k l y ‾ \color{#20A900}{\underline{quickly}} answered 4996.

To confirm, use the formula stated above. :)

Isaac Lu - 6 years, 11 months ago

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