A bag contains 6 balls each of red, blue, green and yellow colours. In how many ways can 4 balls be drawn from the bag?
(a) In how many of the selections, the balls drawn are of the same colour?
(b) In how many of the selections the balls drawn are all of different colours?
Solution not provided.
Ans. 14
There are 14 points in a plane, 7 of which are collinear. How many
(a) straight lines (b) triangles can be formed by these points?