The sum of the first ten terms of an arithmetic Progression is 400. If the sum of the first 6
terms of the same series is 120, find the 15th term.

345.

Explanation:

Sum of n terms = n/2[2a1 + (n-1)d]

So 400 = 10/2(2a1 + 9d) and

120 = 3(2a1 + 5d)  so we have the system:

400 = 10a1 + 45d A

120  = 6a1 + 15d    B         multiply this by 3:

360  = 18a1 + 45D     Subtract this from equation A:

40 = -8a1

a1 = -5

So plugging this value into B:

d =  (120 - 6*-5) / / 6

= 150/6 = 25.

15th term = a1 + (n - 1)d

= -5 + (15-1)25

=  345.

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people like to have money.

i am tired.

it is getting late.

in   ¨and yet the books¨   by czelaw miloz the tone is positive since it tells us that when we touch a book, it starts to live and the perspective is in the third person and turns once into the first person. in "the rhinoceros" by eugene ionesco the tone is illogical and absurd   and the perspective is in the third person since it is a play.