Expanding Brackets on Mathigon

 

Black and White Areas

 Find the difference between black and white areas.

via @mathlava

Three-digit combination

via Puzzle A Day

 

How Many Nines?

 

How many nines will there be in the product of the above multiplication operation?

What is a shorter way of answering this problem?

Newsletter Issue 4

 

 

 

Significant Figures - Issue 4 [Download]

Quarter and a half

 

Next One?

 

The Door Number

Eda and Ece are invited by Naz, who is a new neighbour in their housing. They accept the invitation and ask for the room number.

Naz replies as;

My room number is one of the following ten numbers:

43, 45, 36, 39, 23, 24, 26, 14, 15, 10

Then she whispers to Eda the tens digit of the number, and similarly, Ece learns the other digit. 

Eda says: "I don't know Naz's door number, but Ece, you also don't know."

Ece replies: "You are right, I didn't know, but now I know it."

Eda: "Hmm, then I also know what it is now."

What do you think is the door number?

I was asked this question by a colleague in a van during a trip, and we had quite a good time trying to solve it. I realized that it was a popular question on Turkish social media and forums a few years back. Unfortunately, I could not find the owner of the problem.

Odd One Out

 

Choose the odd one out! 

 

 

 

 

 

 

 

 

 

 

hint: cubic numbers +2

Worn Out Numbers

 

 

 

 

(taken from)

Forward, Left and Right

 

Librarian's Nightmare

Divide the shape below, which looks like an open book, into two identical pieces. (In other words, if the shape was made of paper, how do you cut it so that you get two identical pieces with no extra material left over. Pieces may be flipped over.) 

 

 

 

 

(resource and more at Monday's Puzzle)

Newsletter - Issue 3

 

Significant Figures - Issue 3 [Download]