Multiplying+and+Dividing+Decimals

CHAPTER 5.5-5.8 revision by Aidan

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=multiplication and devision by multiples of 10=

Using place value we can see what happens when we multiply or divide a decimal by 10, or 100, or 1000, and so on. When multiplying a decimal by 10 or 100 or 1000 .. . we move the decimal point to the right as many places as the number of zeros. When dividing a decimal by 10 or 100 or 1000 .. . we move the decimal point to the left as many places as the number of zeros.

=multiplication of decimals= Multiplication of decimals is the same as most other multiplication, first you remove the Decimal like so 14.74 1474 __X 2__ becomes X 2 Then it is a simple multiplication. 1474 __X 2__ 2948 Then you add the decimal in its old position so the answer goes from 2948 to 29.48

If both the numbers contain decimal places it becomes a bit different... If the equation look like this 45.2 you start by again removing the decimals. __X 9.4__ So it should look like this 452 see it is simple X 94 Now you do the math to get the result of 42488 Now comes the trickiest part because there are two decimal places you put the point two places in the answer so the final product is... 424.88 see simple.

=devision of decimals= RULES- __for example,0.04)3.245 becomes 4)3245__ __then the answers are easy to calculate__ __eg.__ 2)4.888 we know that four is easy to devide by two and so is eight so the answer will look like this: __2.444__ 2)4.888
 * **devision by a whole number**- the decimal point in the answer will be directly above the decimal point in the number you are dividing.
 * **devision by a decimal fractions-** move the decimal point of both numbers the same number of places to the right so the number you are dividing by is a whole number. _

=applications of decimals using the calculator= STEPS FOR SOLVING PROBLEMS (on most tests numbers like 4537.98479367467753264 are too long so we round them down to 4537.98
 * 1) Understand the problem: What am I given and what am I asked to find
 * 2) Decide on a method
 * 3) Write a mathmatical statement
 * 4) Estimate the answer if necessary
 * 5) Determine your answer
 * 6) Chech that the answer is reasonable and round off if necessary

revision questions
1. 234.6 divided by 5 2. 9865.345 times 9 3. 2867.436 divided by 5.43 4. divide 435532.535 by 365.534 then round to two decimal places 5. 6155X468

ANSWERS 1= 46.92 2= 88,788.105 3= 528.0729281767956 (round down to 528.07) 4= 1,191.50 5= 2,880,540