Q9 of 47 Page 1

How many terms of the A.P. 18, 16, 14, … be taken so that their sum is zero?

It is given in the question that,

1st term, a = 18


Common difference, d = 16 – 18 = -2


Also, Sn = 0


We know that,



0 = n (19 – n) = 0


∴ n = 0 or n = 19


As total number of terms cannot be zero therefore n will be equal to 19


Hence, number of terms, n = 19


More from this chapter

All 47 →
7

In Fig. 2, a circle is inscribed in a ΔABC, such that it touches the sides AB, BC and CA at points D, E, and F respectively. If the lengths of sides AB, BC and CA are 12 cm, 8 cm and 10 cm respectively, find the lengths of AD, BE and CF.

 8

The x-coordinate of a point P is twice its y-coordinate. If P is equidistant from Q(2,-5) and R(-3,6), find the coordinates of P.

 10

In Fig. 3, AP and BP are tangents to a circle with center O, such that AP = 5 cm and ∠APB = 60 °. Find the length of chord AB.

 11

In Fig. 4, ABCD is a square of side 14 cm. Semi-circles are drawn with each side of the square as diameter. Find the area of the shaded region.