Question

Find the 15th term from the last of the A.P. 5, 12, 19, ........... 250.

Answer 1

here is your Answer:-

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first term a= 5

common difference d = 12-5= 7

last term an= 250

no of terms n

using formula

an = a+(n-1)×d

250 = 5 +( n-1)×7

245= 7n -7

252=7n

n= 252/7 = 36

15 last term will be 36 -15 = 21 from starting

so

15th term from last = 21 term from begining

21st term = a+20d. = 5 + 20× 7

= 5 + 140 = 145

hence 15th term from the last of the AP is 145