**Sequence and Series Session-1**

**Try these Problems :**

- The sum of the three consecutive numbers in GP. is 21 and the sum of their squares is 189. The product of the numbers is

(A) 72 (B) 216 (C) 108 (D) 144

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**Sequence and Series Session-2**

Basic concepts and problems on arithmetic, geometric and harmonic progression have been discussed in the video lecture. Useful for the students appearing for competitive exams.

**Try these problems :**

- If the sides of a right angled triangle form an A.P. then the sines of the acute angle is

(a) 3/5, 4/5 (b) 3/4, 3/5 (c) 2/5, 3/5 (d) none of these

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**Sequence and Series Session-3**

Problems from previous year papers have been discussed in the session.

A progression is called a harmonic progression (H.P.) if the reciprocals of its terms are in A.P.

Standard form: 1/a, 1/(a +d), 1/(a +2d) ......... 1, 1/2, 1/3, ......... are in harmonic progression and 1, 2, 3..... are in arithmetic progression.

**Harmonic Mean:**

If three or more numbers are in H.P., then the numbers lying between the first and last are called harmonic means (H.M.’s) between them. For example 1, 1/3, 1/5, 1/7, 1/9 are in H.P. So 1/3, 1/5 and 1/7 are three H.M.’s between 1 and 1/9.

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