Question

Which term of the A. P. 5,13, 21 ---- is 181 ?

25

24

23

32

​

Answer 1

• 23th term of AP is 181 .

Step-by-step explanation:

To Find :

• which term of Given AP is 181.

Given :

• AP = 5 ,13, 21

Solution :

• First term (a) = 5

Common difference :

• a2 = 13
• a1 = 5

»a2 - a1 = 13 - 5

»a2 - a1 = 8

»a3 - a2 = 21 - 13

»a3 - a2 = 8

• »a2 - a1 = a3 - a2 = 8

So,

• Common difference (d) = 8

As we know that,

$\underline{ \red{ \boxed{\boldsymbol{ { \purple\star }\: a_n = a + (n - 1)d}}}}$

Now,

• an = 181
• a = 5
• d = 8
• n = ?

⇒181 = 5 + (n - 1)8

⇒181 - 5 = (n - 1)

⇒176/8 = (n - 1)

⇒22 = n - 1

⇒ 22 + 1 = n

• n = 23

Hence ,

• 〈 $\bf{\dag\:23th \:term \:of \:AP \:is\: \red{181}}$ 〉

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Answer 2

Answer:

c) 23

Step-by-step explanation:

an = a + (n - 1)d

an = last term = 181

a = first term = 5

d = common difference = 8

n is number of terms which we have to find

Simply substitute the values,

→ 181 = 5 + (n - 1)8

→ 181 - 5 = (n - 1)8

→ 176 = (n - 1)8

Divide by 8 on both sides,

→ 176/8 = (n - 1)8/8

→ 22 = (n - 1)

→ 22 + 1 = n

→ 23 = n