| How do you know what to do first in this expression? |
|---|
| 2 × 3 + 3 = x |
| Maybe it’s addition first, then multiplication. Adding first gets you . . . |
| 2 × 3 + 3 = 12 WRONG! |
| Or, maybe it’s multiplication first, then addition. Multiplying first gets you . . . |
| 2 × 3 + 3 = 9 Right! |
| And then you set fire to your math book before it gets more complicated, like . . . |
| 7 + (2 × 32 + 3) = x |
| Learn this word to help you: PEMDAS: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction |
| Perform the operations in parentheses first. Of course, that means you have to do other operations. Start with exponents. |
| 7 + (2 × 32 + 3) = x |
| 7 + (2 × 9 + 3) = x |
| Then multiplication/division |
| 7 + (18 + 3) = x |
| Then addition/subtraction |
| 7 + (21) = x |
| Finally, add the parentheses to the remainder of the expression. |
| 28 = x |
Most importantly, remember Exponents, Multiplication/Division, Addition/Subtraction
- 2 × 3 + 3 =2 × 3 + 3 = 9
- 2 + 3 × 3 =2 + 3 × 3 = 11
- 3 × 4 + 2 =3 × 4 + 2 = 14
- 3 + 4 × 2 =3 + 4 × 2 = 11
- 2 + 32 × 2 =2 + 32 × 2 = 20
- 32 × 2 - 2 =32 × 2 - 2 = 16
| You may have heard that you should go from left to right. This is true within multiplication/division, for example. |
|---|
| 12 ÷ 3 × 4 = 16 Right! |
| If you go right to left, you get |
| 12 ÷ 3 × 4 = 1 WRONG! |