I often introduce new puzzles to my kids. I believe puzzles have many essential benefits for them. It strengthens their ability to persevere and think critically to solve the problems. To understand triangular number, we created a puzzle using coin. Do you know that numbers can have shapes as well? For instance, the number 10 is a triangular number because ten identical objects can be arranged in an equilateral triangle. Doing so would result in a triangle with four of these objects on each side. Can you generate any additional triangular numbers? Would 3, 6, or 16 work?

**WHAT IS A TRIANGULAR NUMBER**

Triangular numbers are the numbers

A number is called a triangular number if the same number of dots or objects can be arranged to form an equilateral triangle. For example, the numbers 1, 3, 6, 10 and so on can be arranged to form a triangular number sequence.

As you can see from the bottom row of dots, each triangle comes from the one before by adding one more dot. These are called triangular number sequence.

**TRIANGULAR NUMBER PUZZLE USING COINS**

For this puzzle, place 10 pennies on a flat surface in the shape of a triangle. Just by moving three pennies, turn it into a triangle that points in the opposite direction.

**HOW TO SOLVE THE COIN PUZZLE**

We know that the triangular number 10 has 4 coins in the bottom row and 1 in the topmost row. To make the triangle point in the opposite direction, we need to make the second row have 4 coins and move the coin in the first row to the the fourth row. Here are the steps

Move the rightmost penny in the fourth row to the rightmost column of the second row.

The leftmost penny in the fourth row moves to the leftmost column of the second row.

The one penny in the top row moves to the row in front of the two pennies left in the fourth row.

Voila , your triangle is now facing in the opposite direction.

**RELATED POST : 30+ MATH PUZZLES AND ACTIVITIES FOR KIDS**

**MORE COIN PUZZLES AND BRAIN TEAER BOOKS**

If you enjoyed doing the coin puzzle, here are some more puzzles using coins

And here are some good puzzle books to have in your book shelves.

( Disclosure : This post contains affiliate links, meaning, at no cost to you, I earn commission if you click through and make a purchase )

The puzzles in the book 125 Best Brain Teasers of all time cover 5 levels of difficulty and there are a variety of wordplay, math, and logic brainteasers. Some of the problems have related short historical facts. I found that few of the brain teasers are redundant. And , for some questions there can be multiple solutions but only one solution is given. It gives you a chance to work your brain and find them out yourself.

There are 78 riddles in the book Of Course ! The Greatest Collection of Riddles & Brain Teasers For Expanding Your Mind and I love how each riddle is unique and engaging which keeps the content fresh. The riddles are easy to read and understand. The questions are crafted in such a way that they prompt you to think and there comes a moment of clarity where you say “of course!” . Overall, it is a fun book your kids would enjoy.

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