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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.
X  1  2  3  4  5  6  7  8  9  10  11  12 
1  1  2  3  4  5  6  7  8  9  10  11  12 
2  2  4  6  8  10  12  14  16  18  20  22  24 
3  3  6  9  12  15  18  21  24  27  30  33  36 
4  4  8  12  16  20  24  28  32  36  40  44  48 
5  5  10  15  20  25  30  35  40  45  50  55  60 
6  6  12  18  24  30  36  42  48  54  60  66  72 
7  7  14  21  28  35  42  49  56  63  70  77  84 
8  8  16  24  32  40  48  56  64  72  80  88  96 
9  9  18  27  36  45  54  63  72  81  90  99  108 
10  10  20  30  40  50  60  70  80  90  100  110  120 
11  11  22  33  44  55  66  77  88  99  110  121  132 
12  12  24  36  48  60  72  84  98  108  120  132  144 
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, rearranging 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.
10^{3} x 10^{4} = 10^{7}
10^{3} x 10^{4} = 10
10^{0} = 1
10^{3} x 10^{2} = 10^{5}
1 / 10^{3} = 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 nonstandard.
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 "Timestentothe" 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 10^{3} 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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