GRE Quantitative Reasoning › How to find order of operations
Evaluate:
3 + 2(1 * 9 + 8) – 9/3
76/3
82
37/3
36
34
Order of operations
Do everything inside the parenthesis first:
3 + 2(17) – 9/3
next, do multiplication/division
3 + 34 – 3
= 34
3 + 4 * 5 / 10 – 2 =
1.5
3
5
5.5
7
Here we must use order of operations. First we multiply 4 * 5 = 20. Then 20 / 10 = 2. Now we can do the addition and substraction. 3 + 2 – 2 = 3. If you started at the beginning on the left hand side and not used order of operations, you would mistakenly choose 1.5 as the correct answer.
Order of operations can be remembered by PEMDAS (Please Excuse My Dear Aunt Sally): Parentheses Exponents Multiplication Division Addition Subtraction.
\[7(5 + 2) – (5 * 8)\]2 =
1: Inner parentheses = \[ 7(7) – 40 \]2
2: Outer brackets = \[ 49 – 40 \]2 = 92
3: Exponents = 81
This looks daunting as one long equation, but let's look at each piece and then add them all together.
2–3 = 1/23 = 1/8
250 = 1
(–218)1 = –218
6251/4 = 5
(–27)1/3 = –3
Then, 2–3 + 250 + (–218)1 + 7/8 – 6251/4 + (–27)1/3 = 1/8 + 1 – 218 + 7/8 – 5 – 3 = –224.