Question

The first term of an arithmetic sequence is 21 and its 11th term is 121. What is its 15th term

Answer 1

Given :

• First Term (a) = 21

• 11th Term = 121

To find :

• Its 15th term

Solution :

First find D common difference :

• As we know

=> 11th term = a + 10d

=> 121 = 21+ 10d

=> 100= 10 d

=> d = 10

Now ,

• 15th term

=> a + 14d

=> 21 + 14(10)

=> 21 + 140

=> 161 .

Answer 2

Answer:

$\large \dag$ Question :-

The first term of an arthematic sequence is 21 and its 11th term is 121.What is its 15th term .

$\large \dag$ Answer :-

$\large \dag$ The 15th term of an AP is 161

$\large \dag$ Solutions :-

Hey mate ,

In the question given that,

• a=21 (First term)
• 11th term of an AP =121.

According to the given question, we should find 15th term of an AP.

So,

• First here lets calculate the value of d (Common difference) and then we can find 15th term of an AP.

Now,

• 11th term of an AP = a +10d
• 121 =21 +10d
• 121 - 21 =10d
• 100 = 10d
• 100/10 = d
• 10 = d.

Now ,

• According to the given question we should find 15th term of an AP.

So,

• 15th term of an AP = a + 14d
• 15th term of an AP = 21 + 14(10)
• 15th term of an AP = 21 +140
• 15th term of an AP = 161.

Therefore,

• This is the perfect answer to your question..

Hope it helps u mate.

Thank you .