## Planting Trees on Arbor Day

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?

Ten. The fifth-graders planted five more trees than they were assigned, and the fourth-graders planted five fewer than their assignment.

## Sunny Weather Coming?

It’s raining at midnight. Will there be sunny weather in 72 hours?

No, because in 72 hours it will be midnight again.

## Three Kinds of Apples

Three kinds of apples are mixed randomly in a box. How many apples must you take out to be sure of having at least two apples of one kind?

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 Under a Tree

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.

## The Horse and the Plane

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**.

## Kaitlyn’s Age Plus and Minus Three

Kaitlyn’s age plus three has an integer square root. Three years ago, Kaitlyn’s age was the square root.

How old is Kaitlyn?

Kaitlyn is 6 years old.

6 + 3 = 9, and 9 has an integer square root.

6 – 3 = 3, and 3 is the square root of 9.

## What Word Could Be Added to Make New Words?

What word could be added to all of these words?

apple

cone

lake

tree

ridge

nuts

Pine.

## A Third of the Way But Only Halfway There

You’ve traveled a third of the way, yet you’re only halfway there.

Where are you going?

Hint: The answer applies in the US but not in Europe.

You’re in a build headed to the fourth floor. When you reach the second floor, you’ve gone one floor and have two more floors left, so you’re 1/3 of the way. But at the same time, you’re on the 2nd floor and have two more floors to get to the 4th floor, thus you’re halfway there.

This doesn’t work in Europe, because they typically refer to the “first floor” as the ground floor, and the first floor is one story up.

Thanks to Danny Llinas for submitting this.

## Silent Military Communication

How could a member of the military communicate silently and without light?

By using braille.

Braille was based on a tactile military code called night writing, developed by Charles Barbier in response to Napoleon’s demand for a means for soldiers to communicate silently at night and without light. In Barbier’s system, sets of 12 embossed dots encoded 36 different sounds. It proved to be too difficult for soldiers to recognize by touch and was rejected by the military.

## What’s Special About 854,917,632?

What is special about the number 854,917,632?

It is the numbers from one to nine in alphabetical order.

Eight, Five, Four, Nine, One, Seven, Six, Three and Two.