Combination & Probability (2)( Week 42 Practice) 1. Susan spent exactly $3.60 for some 23-cent stamps and 15-cent stamps. How many stamps did she buy in total? 2. There are 9 cards with numbers 0, 2, 3, 4, 5, 6, 7, 8, and 9 on them. These 9 cards were put in a box. You are asked to randomly pick up two cards each time to form a two-digit number (Cards are then put back). How many different two-digit numbers can you form? 3. There are 12 socks in a drawer. Among them, 4 are black, 3 are white and 5 are blue. Nick picks one sock from the drawer (without returning it), and it is black. He picks another one (without returning it), and it is white. If he randomly picks the third sock from the drawer, what is the probability that the sock is blue? 4.
If one of the figures above is selected at random, what is the probability that the number of sides in the selected figure will be less than 8? 5. Steve has the following coins in his pocket: 2 pennies, 1 nickel, 1 dime, 1 quarter, and 3 half-dollars. 6 of these coins are taken out of the pocket and the sum of their values is recorded. How many different sums are possible? |