Multiply by 5 In Your Head

mental-math

Multiplying by 5 mentally is easy since you just divide the number to be multiplied by 2 and multiply the result by 10, (also very simple, by just adding 1 zero to the number or if the number has a .5, just move one decimal place to the right).

Examples:

34 × 5

Thought Process:

1. 34 ÷ 2 = 17

2. 17 × 10 = 170

Therefore, 34 × 5 = 170

63 × 5

Thought Process:

1. 63 ÷ 2 = 31.5

2. 31.5 × 10 = 315

Therefore, 63 × 5 = 315

There are many posts about more sophisticated mental multiplication techniques coming up, though I have to cover the basics first for the sake of completeness.

About Edmark M. Law

My name Edmark M. Law. I work as a freelance writer, mainly writing about science and mathematics. I am an ardent hobbyist. I like to read, solve puzzles, play chess, make origami and play basketball. In addition, I dabble in magic, particularly card magic and other sleight-of-hand type magic. I live in Hong Kong. I blog at learnfunfacts.com. You can find me on Twitter @EdmarkMLaw and Facebook. My email is learnfunfacts@gmail.com
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25 Responses to Multiply by 5 In Your Head

  1. wandaintn says:

    My husband does it this way, but I get confused when I try it. I’ll stick with the way I was taught in grade school, my brain doesn’t handle change very well! 😉

    Liked by 1 person

  2. Brilliant, Edmark. This method is great for my 10-year old daughter. ᕕ( ᐛ )ᕗ

    Like

  3. parkinsons95 says:

    Where were you when I needed you in my school years??? Lol. This is awesome. Never to late to learn!

    Liked by 1 person

  4. parkinsons95 says:

    Too late. I need help with grammar, TOO!

    Liked by 1 person

    • From what I’ve seen from your posts, your grammar is good.

      While I’ll never accept even minor grammatical errors on academic papers, it’s not that big of a deal in other types of writings as long as you don’t commit basic errors, and your writings are not ambiguous.

      Besides, the English language is a continuously evolving language and it is mostly defined by usage instead of a fixed set of stringent and encompassing rules.

      Like

  5. Lilly Moore says:

    That’s a cool method, I never thought of doing that 🙂

    Liked by 1 person

  6. Oh! I loved this one. I just didn’t knew this one. Thank you, for sharing such a magical way to multiply anything by 5.

    Liked by 1 person

  7. Shivangi says:

    Wow you are incredible! Thank you for following me… am so happy to follow you back😀

    Liked by 1 person

  8. This was handy! Thanks for sharing🤗

    Liked by 1 person

  9. parkinsons95 says:

    Helpful! Once again, I needed this years ago. Lol

    Liked by 1 person

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