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Find the 20th term from the last term of the A.P. 3, 8, 13, …, 253 - CBSE Class 10 - Mathematics

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Question

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

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.

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APPEARS IN

 NCERT Solution for Mathematics Textbook for Class 10 (2019 to Current)
Chapter 5: Arithmetic Progressions
Ex. 5.20 | Q: 17 | Page no. 107
Solution Find the 20th term from the last term of the A.P. 3, 8, 13, …, 253 Concept: nth Term of an AP.
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