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Find the 20th term from the last term of the A.P. 3, 8, 13, …, 253 - Mathematics

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Find the 20th term from the last term of the A.P. 3, 8, 13, …, 253

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Solution

Given A.P. is

3, 8, 13, …, 253

Common difference for this A.P. is 5.

Therefore, this A.P. can be written in reverse order as

253, 248, 243, …, 13, 8, 3

For this A.P.,

a = 253

d = 248 − 253 = −5

n = 20

a20 = a + (20 − 1) d

a20 = 253 + (19) (−5)

a20 = 253 − 95

a = 158

Therefore, 20th term from the last term is 158.

Concept: nth Term of an AP
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APPEARS IN

NCERT Class 10 Maths
Chapter 5 Arithmetic Progressions
Exercise 5.2 | Q 17 | Page 107
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