Carol spent exactly $1 for some 5¢-stamps and some 13¢-stamps. How many 5¢-stamps did she buy?
I have a drawer which contains 40 socks in the following numbers and colors: 12 tan, 9 brown, 11 gray, and 8 blue. Suppose I am blindfolded. What is the fewest number of socks I must pick from the drawer to be absolutely certain that I have two socks of the same color among those I have picked?