# CBSE Class 10-Mathematics: Chapter – 5 Arithmetic Progressions Part 21 (For CBSE, ICSE, IAS, NET, NRA 2022)

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**Question 11**:

If the sum of terms of an AP is and its term is , find the value of

**Answer**:

Put

**Question 12**:

If the sum of three numbers in AP, be and their product is , find the numbers.

**Answer**:

Let no. be

**Question 13**:

If are in AP, then prove that are in AP

**Answer**:

Given are in AP

Then

If are in AP then

From (i) and (ii) ,

Hence proved.

**Question 14**:

If be the sum of , and 3n terms respectively of an AP, prove that

**Answer**:

R. H. S