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Rounding off to Whole Numbers - Examples
This is all about the order in which you do a calculation.
For example here are two bits of arithmetic with different meanings ...
3 + 2 x 7 = 17 Do the multiplication first and then add three.
(3 + 2) x 7 = 35 The brackets override the rule above so work out the brackets first and then multiply by seven.
Speed up your calculations by learning your times tables.
Calculate 1/4 + 1/7
Using a calculator with brackets you would enter this ...
1 / 4 + 1 / 7 =
You don't need brackets because the BODMAS rules work without them.
Calculate Rt if the formula is this: 1 / Rt = 1 / R1 + 1 / R2
Using a calculator with brackets you would calculate Rt like this ...
1 / ( 1 / R1 + 1 / R2 ) =
If there are no + or - signs in the formula, re-arranging is easy. Diagonal moves are allowed across the equals sign. This works for most of the formulas for Electronics GCSE up to A Level,
Here is an example ...
Examples - The powers add up.
103 x 104 = 107
10-3 x 104 = 10
100 = 1
10-3 x 10-2 = 10-5
1 / 103 = 10-3
There seem to be several methods used by different calculator manufacturers to solve powers of 10. Most students should use a low cost scientific calculator. More advanced models can be too hard to use and sometimes are quite non-standard.
Find out how to enter powers of 10 into your calculator. The most obvious way is nearly always wrong! Look for the Exp button. This is the "Times-ten-to-the" button. Find the +/- negate button. This is used to enter things like 10-9. If you use the normal minus button, on many calculators, it won't work. On some calculators the Exp button is labelled x10
If the frequency in Hertz = 1 / (2 π R C), to the nearest Hertz, calculate the frequency if R = 84 kilohms and C = 3 nanofarads.
84 kilohms = 84 x 103 Ohms
3 nanofarads - 3 x 10-9 Farads
Here are the calculator key presses for simple scientific calculators ...
1 / ( 2 x PI x 84 Exp 3 x 3 Exp 9 +/- ) =
Your calculator may be different. Learn how to use it! Get help if you need it!
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