D.U. 8: Decimal numbers and monetary system

D.U. 8: Decimal numbers and monetary system

1. Addition and subtraction of decimal numbers

   • We have to add or subtract, hundredths with hundredths, tenths with tenths, units with unit,…
     • Addition
       • When we have 10 hundredths, we have to join them and we will obtain a tenth.
         • When we have 10 tenths, we have to join them and we will obtain a unit.
     • Subtraction
       • When we cannot take some units of the subtrahend from the units of the minuend we have to borrow units from the immediately superior unit and make a transformation (1 unit to 10 tenths or 1 tenth to 10 hundredths)

2. Tenth and hundredth

   • Tenth: The unit has 10 equal parts. Each part is a tenth.
     • • Fraction: 1/10
         • Decimal number: 0,1
   • Hundredth: The unit has 100 equal parts. Each part is a hundredth.
     • • Fraction: 1/100
         • Decimal number: 0,01

3. Monetary system

   • • • Writing: 12,67
         • Decomposition: 1T + 2U + 6t + 7h
           • Reading: 12 units and 67 cents

4. Equivalences

   • There are different ways to represent a quantity of euros using coins and banknotes.

5. Compositions and decompositions

   • There are different ways to represent a number using multibase blocks.

6. Comparing decimal numbers

   • To compare two numbers, we have to compare “unit” by “unit” starting by the unit situated on the left.
     • Warning: A number with less digits in its fractional part can be greater.

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