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Decimal Basics: Place Value, Operations, and Multiplication and Division

Learn the basics of decimals, including place value, addition, subtraction, multiplication, and division. Understand how to line up decimal points, add or subtract decimals, multiply decimals without considering decimal points, and divide decimals by converting them into whole numbers. Practice rounding decimals to a sensible number of figures.

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Decimal Basics: Place Value, Operations, and Multiplication and Division

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  1. Decimals are my thing You see them all around Temperature, time, receipts and bills They're even in the pound! Can you think of any more examples?

  2. DECIMALS DECIMALS

  3. PLACE VALUE

  4. MULTIPLYING BY 10, 100 ,1000

  5. DIVIDING BY 10, 100 ,1000

  6. ADDITION AND SUBTRACTION • LINE UP DECIMAL POINTS EXACTLY • ADD OR SUBTRACT THE SUM E.g. 2.34 + 18.034 and 234 – 3.56 18.034 234 +2.34 - 3.56

  7. MULTIPLICATION • 3.45 x 2.1 • Ignore the decimal points • Multiply as normal • Put the decimal point back into the answer 345 x21 Put the decimal point back into the answer. Look at the question, there are 3 numbers after the decimal place so work the decimal place back into the answer.

  8. Division • To divide a whole number into a decimal • Divide as normal • Keep the decimal points in line • Round the answer to sensible number of figures where necessary E.g. 172.6 ÷4 Keep the decimal points in line 4 Add 0s to the end if need be Note – check by multiplication

  9. Divide a decimal by a decimal • Change the number you are dividing by into a whole number. • Do this by multiplying by 10, 100, 1000 • Do exactly the same to the number you are dividing • Divide to find the answer

  10. continued E.g. 7.4 ÷ 0.05 Multiply the 0.05 by 100 to make it into a whole Number. Then do the same to 7.4. 5 Check by multiplication – 148 x 0.05 = 7.4

  11. continued • Find 31.52 ÷2.4 Multiply 2.4 x 10 = 24 Multiply 31.52 x 10 = 315.2 2 4 3 1 5 . 2 = 13.133333333333333333333333 So we round to 13.13 (to 2 dp)

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