## Fast and Simple Math Tricks You Wish You Always Knew Did you know these easy and quick math techniques?

Whether or not you are in civil engineering, don’t you wish you had known these math tricks when you were younger?

#### The Butterfly Method

Believe it or not, if you are subtracting fractions, you can easily find the answer by drawing a butterfly. As seen in this article’s image, the red lines form the shape of a butterfly.

Multiply across and write the answers in the butterfly’s antenna. In this example, 3 x 5 = 15 and 4 x 2 = 8.

Subtract these two numbers to get the answer’s numerator: 7.

Multiply the two denominators, to get the answer’s denominator: 20.

#### Converting Celsius to Fahrenheit and from Fahrenheit to Celsius

From Celsius to Farenheit

Multiply the temperature by 2, then add 30. This gives a good, rough estimate.

For a more precise result, multiply by 1.8 and add 32.

From Farenheit to Celsius

Subtract 30 from the temperature, then divide by 2. This gives a good, rough estimate.

For a more precise result, subtract 32 then divide by 1.8.

### Memorizing π

Remember the first 7 digits of Pi by counting the letters of each word in this sentence: “How I wish I could calculate Pi”

3.141592

### The Multiply by 9 Table

Notice the sequential order of the first and last digits in the answer. First 0 through 9 and then 9 through 0.

9 x 1 = 09

9 x 2 = 18

9 x 3 = 27

9 x 4 = 36

9 x 5 = 45

9 x 6 = 54

9 x 7 = 63

9 x 8 = 72

9 x 9 = 81

9 x 10 = 90

#### Multiplying by 11

Example problem: 11 x 43 = ?

The first and last digit of the answer is the same as the number being multiplied by 11. Add them together to get the middle digit of the answer.

Step 1: 4 3

Step 2: 4 + 3 = 7