We can use place value to subtract two-digit whole numbers easily.

As an example, let's find the following difference:

65-42

First, we line up our numbers (ones over ones and tens over tens):

Tens Ones
\color{red}6 \color{blue}5
\color{red}4 \color{blue}2

Next, we proceed by subtracting the numbers in each place value (from right to left) and writing the results below:

Step 1. Subtracting the ones, we get {\color{blue}5} - {\color{blue}2} = {\color{blue}3}{:}

Tens Ones
\color{red}6 \color{blue}5
\color{red}4 \color{blue}2
\color{blue}3

Step 2. Subtracting the tens, we get {\color{red}6} - {\color{red}4} = {\color{red}2}{:}

Tens Ones
\color{red}6 \color{blue}5
\color{red}4 \color{blue}2
\color{red}2 \color{blue}3

Therefore, we conclude that

65-42 = 23.

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Drawing place value charts each time we want to subtract a pair of numbers isn't very convenient. For this reason, we usually follow a simplified process called the standard algorithm.

Let's once again consider the following difference:

65-42

First, we line up our numbers as follows: (ones over ones, and tens over tens):

\begin{array}{cccccccc} & & \!\!\!\! 6 \!\!\!\!& \!\!\!\! 5 \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 4 \!\!\!\!& \!\!\!\! 2 \!\!\!\! \\ \hline & & & & \end{array}

Next, we proceed by subtracting the numbers in each place value (from right to left):

Step 1. Subtracting the ones, we get {\color{blue}5} - {\color{blue}2} = {\color{blue}3}{:}

\begin{array}{cccccccc} & & \!\!\!\! 6 \!\!\!\!& \!\!\!\! {\color{blue}5} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 4 \!\!\!\!& \!\!\!\! {\color{blue}2} \!\!\!\! \\ \hline & & \!\!\!\! \!\!\!\!& \!\!\!\! {\color{blue}3} \!\!\!\! \end{array}

Step 2. Subtracting the tens, we get {\color{red}6 } - {\color{red}4} = {\color{red}2}{:}

\begin{array}{cccccccc} & & \!\!\!\! {\color{red}6} \!\!\!\!& \!\!\!\! 5 \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! {\color{red}4} \!\!\!\!& \!\!\!\! 2 \!\!\!\! \\ \hline & & \!\!\!\! {\color{red}2} \!\!\!\!& \!\!\!\! 3 \!\!\!\! \end{array}

Therefore, 65 - 42 = 23.

FLAG

Find the value of 84 - 31.

EXPLANATION

First, we line up our numbers (ones over ones and tens over tens):

\begin{array}{cccccccc} & & \!\!\!\! 8 \!\!\!\!& \!\!\!\! 4 \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 3 \!\!\!\!& \!\!\!\! 1 \!\!\!\! \\ \hline & & & & \end{array}

Next, we proceed by subtracting the numbers in each place value (from right to left):

Step 1. Subtracting the ones, {\color{blue}4} - {\color{blue}1} = {\color{blue}3}{:}

\begin{array}{cccccccc} & & \!\!\!\! 8 \!\!\!\!& \!\!\!\! {\color{blue}4} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 3 \!\!\!\!& \!\!\!\! {\color{blue}1} \!\!\!\! \\ \hline & & \!\!\!\! \!\!\!\!& \!\!\!\! {\color{blue}3} \!\!\!\! \end{array}

Step 2. Subtracting the tens, {\color{blue}8 } - {\color{blue}3} = {\color{blue}5}{:}

\begin{array}{cccccccc} & & \!\!\!\! {\color{blue}8} \!\!\!\!& \!\!\!\! 4 \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! {\color{blue}3} \!\!\!\!& \!\!\!\! 1 \!\!\!\! \\ \hline & & \!\!\!\! {\color{blue}5} \!\!\!\!& \!\!\!\! 3 \!\!\!\! \end{array}

Therefore, 84 - 31 = 53.

FLAG

$25 - 22 =$

a
b
c
d
e

$58-45=$

a
$13$
b
$27$
c
$23$
d
$17$
e
$7$

$55-34=$

a
$11$
b
$21$
c
$19$
d
$29$
e
$12$

Let's consider the following subtraction problem:

45-17

First, we line up our numbers (ones over ones and tens over tens), as before:

Tens Ones
\color{red}4 \color{blue}5
1 7

We have a problem. Since 5 is smaller than 7, we cannot calculate 5-7. So what do we do?

The answer is to take the first number ({\color{red}{4}}{\color{blue}{5}}), "borrow" a ten from the tens place and put it in the ones place, as follows:

\begin{align*} {\color{red}{4}}\, \textrm{tens} + {\color{blue}{5}}\,\textrm{ones} &= {\color{red}{3}}\, \textrm{tens} + {\color{blue}{15}}\,\textrm{ones} \end{align*}

Updating the first row in our table gives the following:

Tens Ones
\color{red}3 \color{blue}15
1 7

Now, we subtract as usual!

Step 1. Subtracting the ones, we get 15-7=8{:}

Tens Ones
\color{red}3 \color{blue}15
1 7
8

Step 1. Subtracting the tens, we get 3-1=2{:}

Tens Ones
\color{red}3 \color{blue}15
1 7
2 8

Therefore, we conclude that

45-17 = 28.

Let's now solve the same problem using the standard algorithm.

FLAG

Once again, we consider the following difference:

45 - 17

To use the standard algorithm, we first line up our numbers (ones over ones and tens over tens):

\begin{array}{cccccccc} & & \!\!\!\! 4 \!\!\!\!& \!\!\!\! 5 \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 1 \!\!\!\!& \!\!\!\! 7 \!\!\!\! \\ \hline & & & & \end{array}

Step 1. We cannot compute 5-7. So, we borrow 1 from the tens place. Then we have 4 - 1 = {\color{red}3} tens and \color{red}15 ones:

\require{cancel} \begin{array}{cccccccc} & & \!\!\!\! \small{\color{red}3} \!\!\!& \!\!\! \small{\color{red}15} \!\!\!\! \\ & & \!\!\!\! \cancel{4} \!\!\!& \!\!\! \cancel{5} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 1 \!\!\!& \!\!\! 7 \!\!\!\! \\ \hline & & \!\!\!\! \!\!\!& \!\!\! \!\!\!\! \end{array}

Subtracting the ones, we get {\color{blue}15} - {\color{blue}7} = {\color{blue}8}{:}

\begin{array}{cccccccc} & & \!\!\!\! \small{3} \!\!\!& \!\!\! \small{\color{blue}15} \!\!\!\! \\ & & \!\!\!\! \cancel{4} \!\!\!& \!\!\! \cancel{5} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 1 \!\!\!& \!\!\! {\color{blue}7} \!\!\!\! \\ \hline & & \!\!\!\! \!\!\!& \!\!\! {\color{blue}8} \!\!\!\! \end{array}

Step 2. Subtracting the tens, we get {\color{blue}3} - {\color{blue}1} = {\color{blue}2}{:}

\begin{array}{cccccccc} & & \!\!\!\! \small{\color{blue}3} \!\!\!& \!\!\! \small{15} \!\!\!\! \\ & & \!\!\!\! \cancel{4} \!\!\!& \!\!\! \cancel{5} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! {\color{blue}1} \!\!\!& \!\!\! 7 \!\!\!\! \\ \hline & & \!\!\!\! {\color{blue}2} \!\!\!& \!\!\! 8 \!\!\!\! \end{array}

Therefore, 45 - 17 = 28.

FLAG

Find the value of 72 - 56.

EXPLANATION

First, we line up our numbers (ones over ones and tens over tens):

\begin{array}{cccccccc} & & \!\!\!\! 7 \!\!\!\!& \!\!\!\! 2 \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 5 \!\!\!\!& \!\!\!\! 6 \!\!\!\! \\ \hline & & & & \end{array}

Next, we proceed by subtracting the numbers in each place value (from right to left):

Step 1. We cannot compute 2 - 6. So, we borrow 1 from the tens place. Then we have 7 - 1 = {\color{red}6} tens and \color{red}12 ones:

\require{cancel} \begin{array}{cccccccc} & & \!\!\!\! \small{\color{red}6} \!\!\!& \!\!\! \small{\color{red}12} \!\!\!\! \\ & & \!\!\!\! \cancel{7} \!\!\!& \!\!\! \cancel{2} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 5 \!\!\!& \!\!\! 6 \!\!\!\! \\ \hline & & \!\!\!\! \!\!\!& \!\!\! \!\!\!\! \end{array}

Now, subtracting the ones, {\color{blue}12} - {\color{blue}6} = {\color{blue}6}{:}

\begin{array}{cccccccc} & & \!\!\!\! \small{6} \!\!\!& \!\!\! \small{\color{blue}12} \!\!\!\! \\ & & \!\!\!\! \cancel{7} \!\!\!& \!\!\! \cancel{2} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 5 \!\!\!& \!\!\! {\color{blue}6} \!\!\!\! \\ \hline & & \!\!\!\! \!\!\!& \!\!\! {\color{blue}6} \!\!\!\! \end{array}

Step 2. Subtracting the tens, {\color{blue}6} - {\color{blue}5} = {\color{blue}1}{:}

\begin{array}{cccccccc} & & \!\!\!\! \small{\color{blue}6} \!\!\!& \!\!\! \small{12} \!\!\!\! \\ & & \!\!\!\! \cancel{7} \!\!\!& \!\!\! \cancel{2} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! {\color{blue}5} \!\!\!& \!\!\! 6 \!\!\!\! \\ \hline & & \!\!\!\! {\color{blue}1} \!\!\!& \!\!\! 6 \!\!\!\! \end{array}

Therefore, 72 - 56 = 16.

FLAG

$56 - 39 = $

a
b
c
d
e

$86 - 69 = $

a
$37$
b
$23$
c
$33$
d
$17$
e
$13$

$94 - 35 = $

a
b
c
d
e
Example: Word Problems

A college basketball team scored 25 fewer points this month compared to last month. If they scored 82 points last month, how many points did they score this month?

EXPLANATION

To find the number of points the team scored this month, we need to find 82-25.

First, we line up our numbers (ones over ones and tens over tens):

\begin{array}{cccccccc} & & \!\!\!\! 8 \!\!\!\!& \!\!\!\! 2 \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 2 \!\!\!\!& \!\!\!\! 5 \!\!\!\! \\ \hline & & & & \end{array}

Next, we proceed by subtracting the numbers in each place value (from right to left):

Step 1. We cannot compute 2 - 5. So, we borrow 1 from the tens place. Then we have 8 - 1 = {\color{red}7} tens and \color{red}12 ones:

\require{cancel} \begin{array}{cccccccc} & & \!\!\!\! \small{\color{red}7} \!\!\!& \!\!\! \small{\color{red}12} \!\!\!\! \\ & & \!\!\!\! \cancel{8} \!\!\!& \!\!\! \cancel{2} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 2 \!\!\!& \!\!\! 5 \!\!\!\! \\ \hline & & \!\!\!\! \!\!\!& \!\!\! \!\!\!\! \end{array}

Now, subtracting the ones, {\color{blue}12} - {\color{blue}5} = {\color{blue}7}{:}

\begin{array}{cccccccc} & & \!\!\!\! \small{7} \!\!\!& \!\!\! \small{\color{blue}12} \!\!\!\! \\ & & \!\!\!\! \cancel{8} \!\!\!& \!\!\! \cancel{2} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! 2 \!\!\!& \!\!\! {\color{blue}5} \!\!\!\! \\ \hline & & \!\!\!\! \!\!\!& \!\!\! {\color{blue}7} \!\!\!\! \end{array}

Step 2. Subtracting the tens, {\color{blue}7} - {\color{blue}2} = {\color{blue}5}{:}

\begin{array}{cccccccc} & & \!\!\!\! \small{\color{blue}7} \!\!\!& \!\!\! \small{12} \!\!\!\! \\ & & \!\!\!\! \cancel{8} \!\!\!& \!\!\! \cancel{2} \!\!\!\! \\ \!\!\!\!-\!\!\!\! & & \!\!\!\! {\color{blue}2} \!\!\!& \!\!\! 5 \!\!\!\! \\ \hline & & \!\!\!\! {\color{blue}5} \!\!\!& \!\!\! 7 \!\!\!\! \end{array}

Therefore, the team scored 57 points last month.

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Practice: Word Problems

Angie is reading a book with $74$ pages. So far, she has read $31$ pages. How many pages does Angie have left to read?

a
$47$ pages
b
$27$ pages
c
$43$ pages
d
$37$ pages
e
$33$ pages
Practice: Word Problems

Pam bought $36$ candies for Halloween. During the day, $18$ trick-or-treaters knocked on her door. Given that each trick-or-treater receives one candy each, how many candies does Pam have remaining?

a
$12$ candies
b
$18$ candies
c
$14$ candies
d
$22$ candies
e
$16$ candies
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