Order of operations -- help me
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Anonymous
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To simplify math expressions, use the acronym PEMDAS, working from left to right within both the acronym and the problem. This tells you the order in which you do each step to simplify the problem.
Parentheses, Exponents, Multiplication, Division, Addition, Subtraction Multiplication and division have equal precedence, so if both multiplication and division are present in the problem you simply work your way across the problem from left to right. Do not automatically do multiplication first if division comes first in the problem. For example:30 ÷ 5 × 3 =6 × 3= 18 is correct, but 30 ÷ 5 × 3=30 ÷ 15=2 is wrong. Similarly, once you have reached the last two letters in the acronym, addition and subtraction have equal precedence. If both addition and subtraction are present, do them in the order they appear from left to right. Problem #1: 6^2 - 4* (7-4) First do what is in the Parenthases: 6^2 - 4* (7-4) --> 6^2 - 4* (3) because 7-4=3, so you simplify that part. Second, do Exponents: 6^2 - 4* (3) --> 36 - 4*(3) because 6^2 = 36. Third, do Multiplication: 36 - 4*(3) --> 36 - 12 because 4*3=12. 4*3 and 4*(3) and 4(3) are all ways of writing out the same multiplication problem and they are equivalent to each other. There is no Division or Addition, so simply solve the remaining problem. 36 - 12 = 24 6^2 - 4* (7-4) 6^2 - 4* (3) 36 - 4*(3) 36 – 12 =24 The answer to problem #1 is 24. Problem #2: 5^2 - 4* (5-3) Use the same process as above. First do what is in the Parenthases: 5^2 - 4* (5-3) --> 5^2 - 4* (2) Second, do Exponents: 5^2 - 4* (2) --> 25 - 4*(2) Third, do Multiplication: 25 - 4*(2) --> 25 - 8 There is no Division or Addition, so simply solve the remaining problem. 25 - 8 = 17 5^2 - 4* (5-3) 5^2 - 4* (2) 25 - 4*(2) 25 - 8 = 17 The answer to problem #2 is 17, or c. |
Anonymous
You got the order of operations part correct, but you made an error in your final calculation. 36-12 = 24, not 14. |
Anonymous
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Please
Excuse My Dear Aunt Sally Parenthesis Exponents Multiplication Division Addition for left to right Subtraction from left to right |
Anonymous
| Thanks, all! I'm going to teach that PEMDAS to my DD this weekend when she corrects her test. |
Anonymous
Actually I think that's a bit misleading. Here is how I remember it: 1. Do everything in parentheses. 2. Then do everything with exponents. 3. Then do multiplication/division, from left to right. 4. Then do addition/subtraction, from left to right. |
Anonymous
That's how I learned it too. PEMDAS was written out for us as P E MD AS because multiplication and division have equal rank once you get to that level, as do addition and subtraction, so you simply work across the problem from left to right. |
Anonymous
Not I! I was the first responder who gave an answer -- I solved the problem in the correct order, but subtracted 12 from 36 and got 14! |
Anonymous
Story of my life! |
Anonymous
36 - 4 * 3 ---> 36 - 12
25 - 4 * 2 ---> 25 - 8 |
Anonymous
If multiplication and division have equal rank, then which you do first won't matter whether you do all multiplication and then division and then all addition and then subtraction which means the acronym works PROVIDED THAT you include the "from left to right" for all steps from multiplication to the end. |
Anonymous
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6/2 x 3
Correctly done with multiplication and division equal is 9. However if you did the multiplication first it would be 1. So, it does matter. Multiplication and division are tied and should be done from left to right. |
Anonymous
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Computer programmer here. To avoid confusion with order of operations (from another programme reading the code), we always enclose each clause in () so it's clear what will get executed when.
So instead of 3 * 5 + 2 it's (3*5) + 2 |