Evaluate : 9 + 99 + 999 + …….. upto n terms.

Find the point on the y-axis whose distances from the points (3, 2) and (-1, 1.5) are in the ratio 2 : 1.

If the sum of first 20 terms of an A.P. is same as the sum of its first 28 terms, find the sum of its 48 terms.

If a, b, c are in A.P., show that : (b + c), (c + a) and (a + b) are also in A.P.