# Tag Archives: math

Question: What is one number that’s divisible by everything? and Question: What number is divisible by all 9 numbers 1 to 9? Read more »

## How much purchasing power has the dollar lost over time?

We have heard of inflation, but what is its effect? A dollar doesn’t buy what it used to. But what does that mean? I bought a house in 1988 for \$97,000. If I had to buy it today with a weaker dollar, how much would it cost?

## What is a quick way to add the numbers from 1 to 10, and how does it work?

You can add the integers from 1 to 10 by hand, but what if you need to add from 1 to 1000? The shortcut for adding Read more »

## Are all three digit numbers divisible by eleven and other questions

For example one searcher wonders if all three digit numbers are divisible by eleven. The answer is Read more »

## How to quickly tell if a number is divisible by eleven and why it works

If you add up all the even position digits and also add up all the odd position digits Read more »

## How can you quickly tell if a number is divisible by 7 and why this trick works

This trick isn’t as effective as the test for divisibility by 3. It takes more steps: Read more »

## How can you quickly tell if a number is divisible by 3 and why this trick works

So is 151515151515151515 divisible by 3? I can quickly tell you yes. The trick is to Read more »

## How to win a guess the number of jelly beans in a jar contest

Question: Can you do better than guessing to win a jelly bean counting contest? Answer: Let me count the ways Read more »