SOLUTION: For a given arithmetic sequence, the 42nth term, a42, is equal to 194, and the 88th term, a88, is equal to 424. Find the value of the 10th term, a10.

Algebra ->  Sequences-and-series -> SOLUTION: For a given arithmetic sequence, the 42nth term, a42, is equal to 194, and the 88th term, a88, is equal to 424. Find the value of the 10th term, a10.       Log On


   



Question 1144719: For a given arithmetic sequence, the 42nth term, a42, is equal to 194, and the 88th term, a88, is equal to 424.
Find the value of the 10th term, a10.

Answer by ikleyn(52788) About Me  (Show Source):
You can put this solution on YOUR website!
.
a%5B42%5D = a + 41*d = 194.    (1)

a%5B88%5D = a + 87*d = 424.    (2)


The unknown "a" is the first term, and the unknown "d" is the common difference of the AP.


Thus you have the system of 2 linear equations in 2 unknown, so it is solvable.


The easiest way to solve it is to subtract equation (1) from equation (2). You will get

    87d - 41d = 424 - 194  

    46d       = 230

      d       = 230/46 = 5.


Then from equation (1),  a = 194 - 5*41 = -11.


Now you know EVERYTHING about your AP.  In particular,

    a%5B10%5D = a + 5*9 = -11 + 45 = 34.      ANSWER

Solved.

------------------

There is a bunch of lessons on arithmetic progressions in this site:
    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions
    - One characteristic property of arithmetic progressions
    - Solved problems on arithmetic progressions
    - Calculating partial sums of arithmetic progressions
    - Mathematical induction and arithmetic progressions
    - Mathematical induction for sequences other than arithmetic or geometric

Also,  you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Arithmetic progressions".


Save the link to this textbook together with its description

Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson

into your archive and use when it is needed.


                Come again soon to this forum to learn something new (!)