Some more Arithmetic

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maverik_

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Jun 10, 2013
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Hello,

Thanks for you input on other threads.

I am still struggling but mainly with the following operations. Hoping someone can help me out as to how i can achieve the results in my head with no pen or paper.

Ok......

8/6 *4707

5/9 * 4572

4256/28

272/17 - 12

4238 /16


Now...to many of you this will seem like very easy tasks. To me it's not.....i am warming and improving my mathematics, Im not a kid i'm a grown adult with an important psychometrics assessment to pass which involves 20 mental arithmetic questions.


Thanks all.
 
What are the parameters of the assessment? Shall all this be done in your head? Shall we pursue exact values or approximations? If the latter, how close is required?

What do you know of the "Order of Operations"?
 
maverik_ said:
Hello,

Thanks for you input on other threads.

I am still struggling but mainly with the following operations. Hoping someone can help me out as to how i can achieve the results in my head with no pen or paper.

Ok......

8/6 *4707

5/9 * 4572

4256/28

272/17 - 12

4238 /16


Now...to many of you this will seem like very easy tasks. To me it's not.....i am warming and improving my mathematics, Im not a kid i'm a grown adult with an important psychometrics assessment to pass which involves 20 mental arithmetic questions.


Thanks all.
Click to expand...
I asked you a question similar to tkhunny's on a previous thread. Are rough approximations allowed or are exact answers required? It makes a huge difference. Let me show you why.

Here is how I would do it in my head if I needed an exact answer.

\(\displaystyle \dfrac{5}{9} * 4572 = 5 * \dfrac{4572}{9} = 5\left(\dfrac{4500}{9} + \dfrac{72}{9}\right) = 5(500 + 8) = 2500 + 40 = 2540.\)

In words, it's exactly 2540.

Here is how I would do it in my head if I needed a rough approximation.

\(\displaystyle \dfrac{5}{9} * 4572 \approx \dfrac{5}{9} * 4500 = 2500.\) In words, it's approximately 2500.

If I must find an exact answer in my head I break it down into a series of simpler problems and solve each exactly. It is time consuming and, without paper and pencil, error prone. If I can live with a rough approximation, I break it down into a very simple related but different problem that I can solve exactly without error.

They are different thought processes.
 
tkhunny said:
What are the parameters of the assessment? Shall all this be done in your head? Shall we pursue exact values or approximations? If the latter, how close is required?

What do you know of the "Order of Operations"?
Click to expand...


All done in the head, no pen or paper allowed.

Well i wont be able to do exact values in 10 - 15 seconds. I feel it is just a way to stress me to see how i cope with the next task.

Order of operations - meaning addition, subtraction, multiplication and division?

Thanks
 
maverik_ said:
All done in the head, no pen or paper allowed.

Well i wont be able to do exact values in 10 - 15 seconds. I feel it is just a way to stress me to see how i cope with the next task.

Order of operations - meaning addition, subtraction, multiplication and division?

Thanks
Click to expand...
No. the acronym is PEMDAS

It stands for parentheses, exponentiation, multiplication, division, addition, subtraction.

Calculate what is inside parentheses or brackets first, then do exponentiation going from left to right, then do multiplication and division going left to right, then do addition and subtraction going left to right.

Well if you are not going to try for exact answers, there is no reason for stress. Look for a similar problem with similar but easily computed numbers, do it, and qualify your answer with the word "approximately."

As I told you before, if I am approximating \(\displaystyle \dfrac{5}{9} * 4572\)

I see that 4572 is close to 4500, which is easily divisible by 9 giving 500, and 500 times 5 is 2500. I have an approximate answer, no muss, no fuss.
 
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