1.7 Decimals  (Page 2/10)

Solution

Round 18.379

1. ⓐ to the nearest tenth
   

   Locate the tenths place with an arrow.
   Underline the digit to the right of the given place value.
   Because 7 is greater than or equal to 5, add 1 to the 3.
   Rewrite the number, deleting all digits to the right of the rounding digit.
   Notice that the deleted digits were NOT replaced with zeros.	So, 18.379 rounded to the nearest tenth is 18.4.

   
   
   
2. ⓑ to the nearest whole number
   

   Locate the ones place with an arrow.
   Underline the digit to the right of the given place value.
   Since 3 is not greater than or equal to 5, do not add 1 to the 8.
   Rewrite the number, deleting all digits to the right of the rounding digit.
   	So, 18.379 rounded to the nearest whole number is 18.

Solution

$\begin{array}{cccc}\begin{array}{c}\text{Write the numbers so the decimal points line}\hfill \\ \text{up vertically.}\hfill \end{array}\hfill & & & \hfill \underset{\text{\_\_\_\_\_\_}}{\begin{array}{c}23.5\hfill \\ +41.38\hfill \end{array}}\hfill \\ \\ \\ \begin{array}{c}\text{Put 0 as a placeholder after the 5 in 23.5.}\hfill \\ \text{Remember,}\frac{5}{10}=\frac{50}{100}\text{so}0.5=0.50.\hfill \end{array}\hfill & & & \hfill \underset{\text{\_\_\_\_\_\_}}{\begin{array}{c}23.50\hfill \\ +41.38\hfill \end{array}}\hfill \\ \\ \\ \begin{array}{c}\text{Add the numbers as if they were whole numbers.}\hfill \\ \text{Then place the decimal point in the sum.}\hfill \end{array}\hfill & & & \hfill \begin{array}{c}\underset{\text{\_\_\_\_\_\_}}{\begin{array}{c}23.50\hfill \\ +41.38\hfill \end{array}}\hfill \\ 64.88\hfill \end{array}\hfill \end{array}$

Solution

$\begin{array}{cccc}& & & \hfill 20-14.65\hfill \\ \begin{array}{c}\text{Write the numbers so the decimal points line}\hfill \\ \text{up vertically.}\hfill \end{array}\hfill & & & \hfill \underset{\text{\_\_\_\_\_\_}}{\begin{array}{c}20.\hfill \\ -14.65\end{array}}\hfill \\ \text{Remember, 20 is a whole number, so place the}\hfill & & & \\ \text{decimal point after the 0.}\hfill & & & \\ \\ \\ \text{Put in zeros to the right as placeholders.}\hfill & & & \begin{array}{c}20.00\hfill \\ \underset{\text{\_\_\_\_\_\_}}{\mathrm{-14.65}}\hfill \end{array}\hfill \\ \\ \\ \begin{array}{c}\text{Subtract and place the decimal point in the}\hfill \\ \text{answer.}\hfill \end{array}\hfill & & & \hfill \begin{array}{c}\underset{\text{\_\_\_\_\_\_\_\_\_\_}}{\begin{array}{c}\stackrel{1}{\cancel{2}}\stackrel{\stackrel{9}{\cancel{10}}}{\cancel{0}}.\stackrel{\stackrel{9}{\cancel{10}}}{\cancel{0}}\stackrel{\cancel{10}}{\cancel{0}}\hfill \\ -14.65\hfill \end{array}}\hfill \\ 5.35\hfill \end{array}\hfill \end{array}$