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Adding and subtracting decimals

Adding or subtracting two numbers is simpler in decimal notation than in fractional notation.

  • Write the numbers so that they have the same number of decimal places (putting 0 on the right if needed).
  • Add the numbers in the usual manner, ignoring the decimal point (from right to left).
  • Put back the decimal point at the same position from the right.
\begin{align*} \frac{134}{7} + \frac{12}{5} &= \Tblue{19}.\Tgreen{1}\Tred{4}\Torange{3} + \Tblue{2}.\Tgreen{4}\Tred{0}\Torange{0} = \Tblue{21}.\Tgreen{5}\Tred{4}\Torange{3}\\ \frac{134}{7} - \frac{12}{5} &= \Tblue{19}.\Tgreen{1}\Tred{4}\Torange{3} - \Tblue{2}.\Tgreen{4}\Tred{0}\Torange{0} = \Tblue{16}.\Tgreen{7}\Tred{4}\Torange{3} \end{align*}

Multiplication and division are complex. We normally use a calculator for long multiplication and division methods.