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# Decimals

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### Decimals

1. 1. decimals
2. 2. What is a Decimal?
3. 3. What is a decimal?A decimal is similar to a fraction in that it is not a whole number. It is a part of a number. We use decimals most often when we are talking about money. RS13.45 How would you read this number?
4. 4. RS 13.45THIRTEEN RUPEES POINT FOURTY FIVE PAISE . REMEMBER WE DO NOT USE PAISE WHEN AMOUNT IS less THAN RS 1
5. 5. What does the .45 mean?.45 IS SAME AS SAYING 45 PAISE ITMEANS ONLY A PART OF RUPEES . ITIS NOT WHOLE MONEY. WE STILLNEED TO GET THE WHOLE THING
6. 6. Why do I have to understanddecimals?This is a good question. We need to understand what the value of each number means in order to understand what we are talking about. Here is an exampleHere is an example: A shirt costs RS 12.05, but when I wrote the number down I wrote RS 12.5. What is wrong with this?
7. 7. Why is RS12.5 wrong?RS 12.5 really is saying RS 12.50,because when we read how muchsomething costs it always has two placesafter the decimal point. If we don’t have anumber after the first number we mustassume it is a zero. However, when weread \$12.05, the zero is the place holderso we know it is 5p and not 50p. That is a45¢ difference. I can get a piece of gumfor that amount!
8. 8. How do I read a decimal? If you look at the number 12.3, you say 12 and 3 tenths.If you look at the number and it says 12.35, you say 12 and 35 hundredths.If you look at a number and it says 12.05, you say 12 and 5 hundredths.
9. 9. Let’s Write this in ExpandedNotationIf we are using money, it would look like this:RS100 + RS 30 + RS 7 + 80P + 2 P = RS 137.82. If we are not using money, it would look like this: 100 + 30 + 7 + .8 + .02 = 137.82
10. 10. How do I know how large a decimalis?If you see two numbers that are decimals, one says 7.3 and the other says 7.003, you look at how many places the number that is longer has. You make both numbers the same length by adding zeros to the end of the shorter number. So the numbers read: 7.300 or 7.003 Now when you look at the number you can see which is larger: 7.300
11. 11. Which is larger?1) 4.5 or 4.05Because 4.5 equals 4.50, 50 is larger than 52) 6.003 or 6.3Because 6.3 equals 6.300, 300 is larger than 33) 5.012 or 5.12Because 5.12 equals 5.120, 120 is larger than 12
12. 12. When else do we use decimals?• Weight (He weighed 85.5 lbs)• Temperature (It was so cold today, it was only 43.7 )• Measuring distances (example, the race was a 5 K, but since I don’t understand kilometers, I changed it to miles and saw that the race was 3.1 Miles long)• Can you think of any other times?
13. 13. Addition of decimals• To add decimals, follow these steps:• Write down the numbers, one under the other, with the decimal points lined up• Put in zeros so the numbers have the same length• Then add normally, remembering to put the decimal point in the answer
14. 14. Example: Add 3.25, 0.075 and 5• Line the decimals up: 3.25 0.075 +5 = : 3.250 0.075 +5.000Ans 8 .325
15. 15. Subtracting Decimals• To subtract decimals, follow these steps:• Write down the two numbers, one under the other, with the decimal points lined up.• Add zeros so the numbers have the same length• Then subtract normally, remembering to put the decimal point in the answer
16. 16. Example: Calculate 7.005-0.55Line the decimals up: 7.005 -0.55 = : 7.005 -0.550 ans = 6. 455
17. 17. How to Multiply DecimalsMultiply normally, ignoring the decimalpoints.Then put the decimal point in the answer -it will have as many decimal places as thetwo original numbers combined. In other words, just count up how manynumbers are after the decimal pointin both numbers you are multiplying, thenthe answer should have that manynumbers after its decimal point.
18. 18. Dividing DecimalsTo divide a decimal number by a whole number:Use Long Division (ignoring the decimal point)Then put the decimal point in the same spot as the dividend (the number being divided)
19. 19. Dividing by a Decimal NumberThe trick is to convert the number you are dividing by to a whole number first, by shifting the decimal point of both numbers to the right: It is safe to do this if you remember to shift the decimal point of both numbers the same number of places.