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Q&A #19979 |
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Hi, Ena -- Thanks for writing to T2T. Before you teach any operations with decimals, make sure your students understand the concept of decimals. They need to understand that decimals are fractional parts of a whole, and that each place to the right of the decimal is 1/10 of the place to the left of it. This can be reinforced with money (pennies, dimes, dollars), which children at that age usually understand pretty well. They should be able to combine groups of pennies that can be traded for dimes, and groups of dimes that can be traded for dollars. While doing this, introduce and have students practice the decimal notation that identifies different amounts of money. When teaching the addition and subtraction of decimals, combine and separate various collections of pennies, dimes and dollars so they understand the meaning of the operations in relation to the decimals. Make sure they can order decimals, for example, know that 0.3 is greater in value than 0.12. Also know that extra zeros to the far right do not change the value, e.g., 0.6 is the same as 0.60 and 0.600. Another useful manipulative for decimals is base-10 blocks. The large cube can represent a unit, the flats can be tenths, the longs can be hundredths, etc. If you don't have a good supply of these at hand, there is an interactive applet at http://nlvm.usu.edu/en/nav/frames_asid_152_g_3_t_2.html You can chose which piece represents the unit by changing the decimal places. Play with the "Next problem" function to get some ideas of how you can use these. I hope this helps. Please write again if you have more questions. -Claire, for the T2T service
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