SATHEE: Sequences and Series 2 Question 4

Sequences and Series 2 Question 4

4.

If the sum and product of the first three terms in an AP are 33 and 1155, respectively, then a value of its 11 th term is

(2019 Main, 9 April II)

(a) 25

(b) -36

(d) -35

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Answer:

Correct Answer: 4. (c)

Solution:

Let first three terms of an $A P$ as $a - d, a, a + d$ .

So, $3 a = 33 \Rightarrow a = 11$

[given sum of three terms $= 33$ and product of terms $= 1155]$

$\begin{array}{cc} \Rightarrow & (11 - d) 11 (11 + d) = 1155 \\ \Rightarrow & 11^{2} - d^{2} = 105 \\ \Rightarrow & d^{2} = 121 - 105 = 16 \\ \Rightarrow & d = \pm 4 \end{array}$

So the first three terms of the AP are either 7, 11, 15 or $15, 11, 7$ .

So, the 11 th term is either $7 + (10 \times 4) = 47$

or $15 + (10 \times (- 4)) = - 25$ .

Sequences and Series 2 Question 4

4.

Answer:

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Sequences and Series 2 Question 4

4.

Answer:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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