Question.
Find the 20th term from the last term of the AP 3, 8, 13, ....., 253.
Find the 20th term from the last term of the AP 3, 8, 13, ....., 253.
Solution:
The AP is 3, 8, 13, ..., 253
Its first term = 3 and the common difference = 5.
Now, the AP in the reverse order will have the first term = 253 and the common difference = – 5.
The 20th term from the end of the AP (1)
= The 20 term of the AP in the reverse order
$=a+19 d$
$=253+19 \times(-5)=253-95=158$
The AP is 3, 8, 13, ..., 253
Its first term = 3 and the common difference = 5.
Now, the AP in the reverse order will have the first term = 253 and the common difference = – 5.
The 20th term from the end of the AP (1)
= The 20 term of the AP in the reverse order
$=a+19 d$
$=253+19 \times(-5)=253-95=158$
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