Question

find the number of terms of AP 3,8,13,....253​

Answer 1

Answer:

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Step-by-step explanation:

Given series is 3, 8, 13, ...... 253

here, first term , a = 3

common difference , d = 5

Let us find total number of terms at first.

use \bf{T_n=a+(n-1)d}T

n

=a+(n−1)d

=> 253 = 3 + (n - 1)5

=> 250 = 5(n - 1)

=> n - 1 = 50

=> n = 51

so, there are 51 terms in given series.

now we know, mth term from last =last term - mth term + 1

so, 20th term from last = 51 - 20 + 1 = 32

hence, 20th from last = 32th term from first

use , \bf{T_{32}=a+(32-1)d}T

32

=a+(32−1)d

= 3 + 31 × 5 = 3 + 155 = 158

hence , 20th term from last = 158

Answer 2

Answer:

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