#### What Is Delta in Math? Here’s Everything You Need to Know

Welcome to our beginner-friendly guide to the delta symbol (Δ) in math! Learn about its background, how it’s used in various math subjects, and take a short quiz to test your knowledge.

Mar 2, 2022

Welcome to Mathnasium’s Math Tricks series. When kids learn their multiplication facts, they often first master their five times tables. But multiplying large numbers by five can get tricky. Today we are using the fact that five is *half of ten* to multiply an even or odd number by five.

To calculate any number times five, it can be easier to multiply by ten first and then divide the product by two. Multiplying a whole number by ten follows a simple visual pattern. To divide by two, we rely on our ability to find half of any number. Another option for calculating a number times five is to cut it in half *first*, then multiply by ten.

The general rule for our trick: when we multiply an **even** number by five, we find half first, then multiply by ten, and when we multiply an **odd** number by five, we multiply by ten first, then find half. Follow the examples below as we multiply an even and an odd number by five.

Step 1: Identify the number you are multiplying by five.

72 (even number)

Step 2: Cut the number in half.

Half of 72 = 36

Step 3: Multiply the new number by ten for the final answer.

36 x 10 = 360

Answer: 72 x 5 = 360

Step 1: Identify the number you are multiplying by five.

95 (odd number)

Step 2: Multiply the number by ten.

95 x 10 = 950

Step 3: Cut the new number in half for the final answer.

Half of 950 = 475

Answer: 95 x 5 = 475

Now, with this strategy, you are ready to multiply any even or odd number by five. Click here for more practice problems.

If you missed this or any of our other Math Tricks videos, check them out on our YouTube channel!

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