On Arbor Day the fourth grade class began planting trees. They finished planting five trees before the fifth grade class arrived. But they accidentally planted them on the fifth grade side of the street.
The fourth-graders crossed the street to start over, and the fifth-graders planted the remaining trees. They finished first and felt bad for the fourth-graders, so they crossed the street and planted five trees. They planted another five trees at which point all of the trees had been planted.
By how many trees were the fifth-graders ahead of the fourth-graders?
Four. If the apples are A, B, and C, it’s possible that you could take out one A, one B and one C with three apples, but the fourth apple must be one of the three kinds.
Three philosophers are taking a nap under a tree. While they’re asleep, a small boy smears their noses with red berries. When they awake, they each begin to laugh, thinking the other two are laughing at each other.
But then one philosopher stops laughing, realizing his nose is red too. How did he come to this conclusion?
Let’s call the philosopher’s A, B and C. A reasoned that B was confident his nose wasn’t red. If B saw A’s nose wasn’t red, he would be surprised that C was laughing, because C would have nothing to laugh at. But B wasn’t surprised, therefore, A correctly reasoned his nose was smeared.
A delivery truck from the post office is sent to the airport to meet a cargo plane. The plane lands ahead of schedule, and its contents are brought toward the post office by car. After a half hour, the car meets the truck and they exchange the contents.
The truck returns from the post office 20 minutes early. How early did the plane arrive?
The delivery truck arrived back 20 minutes early, so it would have taken 20 minutes to go from where it met the car to get to the airport and back. Therefore, the car and truck met 10 minutes from the airport. Adding those 10 minutes to the 30 minutes the truck had already driven to meet the car means the plane arrived 40 minutes ahead of schedule.