Question

Which term of the ap : 3, 9, 15, 21, . . . , is 99?

Answer 1

Given,
AP:- 3, 9, 15, 21..........
Tn= 99
Here,
T¹= 3, T²= 9, T³= 15, T⁴= 21, d= 6
So,
Tn= T¹+(n-1)d
99= 3+(n-1)6
96=(n-1)6
96/6= n-1
16+1= n
n= 17
So,
99 is the 17th term of the given AP.

Hope this helps you!

Answer 2

99 is 17th term of AP: 3, 9, 15, 21, . . .

Given:

• An A.P.
• 3, 9, 15, 21, . . .

To find:

• Which term of the ap : 3, 9, 15, 21, . . . , is 99 ?

Solution:

Formula\concept to be used:

General term of AP: $\bf a_n = a + (n - 1)d$

here,

a: First term

d: Common difference

n: number of term

Step 1:

Write the terms to be used in general terms.

Here,

a=3

d= 9-3

d=6

$\bf a_n = 99$

Step 2:

Put the values in formula and find n.

$99 = 3 + (n - 1)6$

or

$6(n - 1) = 99 - 3$

or

$6(n - 1) = 96$

or

$n - 1 = \frac{96}{6}$

or

$n - 1 = 16$

or

$n = 16 + 1$

or

$\bf n = 17$

Thus,

99 is 17th term of A.P.

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