CBSE Class 10-Mathematics: Chapter –5 Arithmetic Progressions Part 3

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Question 11:

Balls are arranged in rows to form an equilateral triangle. The first row consists of one ball, the second two balls and so. On If 669 more balls are added, then all the balls can be arranged in the shape of a square and each of its sides then contains 8 balls less than each side of the triangle. Find the initial number of balls.


Let there be n balls in each side of the triangle

No. of balls in each side square

No. of balls in square


On solving

No. of balls

Question 12:

Find the sum of upto n terms.


upto n terms

Question 13:

If the following terms form a AP. Find the common difference & write the next terms


next three terms

Question 14:

Find the sum of , up to terms


, up to terms

Question 15:

Write the next two terms


Next two terms is ….

Question 16:

If the term of an AP is q and the term is p. P.T its term is