10 Little Hacks From Math Nerds That I Tried And Memorized Because They're So Easy And Useful

10 Little Hacks From Math Nerds That I Tried And Memorized Because They're So Easy And Useful

Recently, I asked the BuzzFeed Community for their best math trick. I'm not talking quantum physics here, but just, you know, an easy way to figure out how much butter I need if I'm doubling a recipe. The answers are remarkably useful, so without further ado, here they are!

Animated characters arguing about math changes, text reads "WHY WOULD THEY CHANGE MATH? MATH IS MATH!"

1."Sales! If something is 70% off, you are paying 30%. If something is $150 on sale for 70% off rather than figure out 10% and multiply by 7 and subtract that from $150."

Handwritten math calculations showing a discount problem, with a pen resting on the paper

2.Find the area of an equal-sided shape by multiplying the center an edge, the length of one side, and half the amount of sides.

Handwritten math notes on finding the area of an equilateral octagon, with a pen resting on the paper

3."Very small and is just a parlor trick, but if you multiply any double-digit number by 11, then you just add the two numbers of the double-digit together and put that in the middle."

Handwritten math equations with mistakes and a pen to the right side
Audrey Engvalson

4."The one that a lot of people find helpful, especially if you cook or bake a decent bit, is the following: multiplying fractions is no problem--top times top (numerator multiplied by numerator) over bottom times bottom (denominator multiplied by denominator)."

Handwritten note solving a math problem to double a recipe that requires 3/8 cup of flour, resulting in 6/8 cup or simplified to 3/4 cup
Audrey Engvalson

5.Divisibility rules are wildly useful.

Handwritten math divisibility rules with a pen resting on the paper

6."Percent can be tricky, especially if you don’t have a calculator, BUT, they’re 'reversible' (not proper math term)."

Handwritten math showing that 18% of 50 equals 50% of 18, both equal 9, with a pen resting on paper

7."To divide by 5 in your head, double the number, then move the decimal point once to the left (divide by 10)"

Handwritten math division problems on lined paper with a pen
Audrey Engvalson

8."When I add, I break it down and do easy first, then hard. So for 25 + 56, I do 25 + 50 = 75 + 6 = 81"

Handwritten math calculations on lined paper with a pen resting on it
Audrey Engvalson

9."The nines multiplication hand trick!"

Handwritten note explaining a multiplication trick for 9 with sketches of hands counting. Summarizes 9x4 using fingers, result is 36
Audrey Engvalson

10."It’s easier to add numbers that end in 0, so kind of a different take on another comment...This especially helps with mental math. You could even take it a next step by saying 39 is “1” away from 40. So instead of adding 73+39, you add 70+40, which is 110, then subtract the “1” and get the final answer of 109."

Handwritten math problem on paper with a calculation mistake corrected for summing 250 and 18, then subtracting 1
Audrey Engvalson

Do you have a math tip you swear by? Tell us all about it in the comments below!