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Chapter 5 · Question 3

How many terms are there in the AP $7,10,13,\ldots,43$ ?

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Answer

Direct Answer

Here

a=7

,

d=3

, and

a_n=43

. Using

a_n=a+(n-1)d

,

43=7+(n-1)3

, so

36=3(n-1)

,

n=13

.

Simple Explanation

Put the last term in the nth-term formula. There are

13

terms.

Exam-Ready Structure

For the AP,

a=7

,

d=3

, and final term

l=43

. Use

l=a+(n-1)d

:

43=7+3(n-1)

. Hence

36=3(n-1)

, so

n-1=12

and

n=13

.

Key Points

Here $a=7$ , $d=3$ , and $a_n=43$ .

Related Questions

State the formula for the sum of first $n$ terms of an AP. Find the sum of first 20 natural numbers.

Reena starts with a monthly salary of ₹8000 and gets an annual increment of ₹500. What will be her salary in the 10th year?

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