Question

Find the 20th term from the last term of the AP:3, 8, 13,...,253.​

Answer 1

Answer:

hlo

your answer is here !

Step-by-step explanation:

$Given series is 3, 8, 13, ...... 253</p><p>here, first term , a = 3</p><p>common difference , d = 5</p><p>Let us find total number of terms at first.</p><p>use </p><p>\bf{T_n=a+(n-1)d}</p><p>=> 253 = 3 + (n - 1)5</p><p>=> 250 = 5(n - 1)</p><p>=> n - 1 = 50</p><p>=> n = 51</p><p>so, there are 51 terms in given series.</p><p>now we know, mth term from last =last term - mth term + 1</p><p>so, 20th term from last = 51 - 20 + 1 = 32</p><p>hence, 20th from last = 32th term from first</p><p>use , </p><p>\bf{T_{32}=a+(32-1)d}</p><p>= 3 + 31 × 5 = 3 + 155 = 158</p><p>hence , 20th term from last = 158$

follow me !

Answer 2

Answer:

from the beginning

a = 3

d = 5

from the ending

a = 253

d = -5

an = a+(n-1)d

a20 = 253+(20-1)*-5

= 253+19*-5

=253-95

=158