Arumour spreads exponentially through a college. 100 people have heard it by noon, and 200 by 1 p. m. how many people have heard it (a) by 3 p. m., (b) by 12.30 p. m., (c) by 1.45 p. rn.?

One card is dealt from a 52 card deck. find the probability that the dealt card is a 4 or a black 7

What is the ratio for the surface areas of the cones shown below, given that they are similar and that the ratio of their radil and altitudes is 4: 3? 23

White shapes and black shapes are used in a game. some of the shapes are circles. while the rest are squares. the ratio of the number of white shapes to the number of black shapes is 5: 11. the ratio of the number of white cicrles to the number of white squares is 3: 7. the ratio of the number of black circles to the number of black squres is 3: 8. work out what fraction of all the shapes are circles.