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

Solution:

The formula for n^th term of an AP is aₙ = a + (n - 1) d

Here, aₙ is the n^th term, a is the first term, d is the common difference and n is the number of terms.

Given A.P. is 3, 8, 13, ..., 253

As the 20^th term is considered from last, so a = 253

Common difference, d = 3 - 8 = - 5 (Considered in reverse order)

We know that the n^th term of an A.P. is aₙ = a + (n - 1) d

So, 20^th Term is a₂₀ = a + (20 - 1)d

a₂₀ = 253 + (20 - 1)(- 5)

= 253 - 19 × 5 

= 253 - 95

= 158

20^th term from the last term is 158.

☛ Check: NCERT Solutions Class 10 Maths Chapter 5

Video Solution:

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

Class 10 Maths NCERT Solutions Chapter 5 Exercise 5.2 Question 17

Summary:

The 20^th term from the last term of the A.P. 3, 8, 13,....., 253 is 158.

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