Mental Math

Mental math means solving math problems in your head. You do not use a pencil, paper, or calculator. With practice and some clever tricks, you can solve problems quickly in your mind.

Tricks and Strategies

There are many mental math tricks. To add 9, you can add 10 and subtract 1. To multiply by 5, multiply by 10 and divide by 2. To subtract, you can count up instead of counting down.

Breaking numbers apart helps too. To add 47 + 36, think of it as 47 + 30 + 6, which is 77 + 6 = 83.

Why Practice Matters

Mental math gets faster with practice. Start with easy problems and work your way up. Try doing simple math in your head when you shop or cook.

Being good at mental math saves time. It also helps you check if answers from a calculator seem right. If a calculator says 5 x 6 = 35, you know something is wrong.

Fun Facts

• Some people can multiply four-digit numbers in their head in just a few seconds.
• Mental math competitions are held around the world.
• The human brain can process simple math facts in about half a second.

Did You Know?

Shakuntala Devi of India was called the human computer. She could multiply two 13-digit numbers in her head in just 28 seconds!