Question

Use the additive inverse to find 23.45−68.7
.

Answer 1

To find \( 23.45 - 68.7 \) using the additive inverse, we can rewrite the subtraction as the addition of a negative number:

\[
23.45 - 68.7 = 23.45 + (-68.7)
\]

Now we need to calculate \( 23.45 + (-68.7) \).

To do this, we can combine the two numbers:

1. Align the numbers for addition:
\[
\begin{array}{r}
23.45 \\
+ (-68.70) \\
\hline
\end{array}
\]

2. Since we are adding a negative number, we can think of it as subtracting \( 68.70 \) from \( 23.45 \).

Now, we can perform the following steps:

- Convert \( 23.45 \) and \( 68.70 \) so that we can subtract:

Let's change \( 23.45 \) to have a matching decimal:

\[
23.45 - 68.70 = 23.45 + (-68.70)
\]

The calculation goes as follows (keeping in mind to borrow when necessary):

1. The larger number \( 68.70 \) is subtracted from \( 23.45 \).
2. Starting from the rightmost digit:

\[
\begin{array}{r}
23.45 \\
- 68.70 \\
\hline
\end{array}
\]

- \( 5 \) (from \( 23.45 \)) cannot subtract \( 0 \) (so remains \( 5 \)).
- \( 4 \) cannot subtract \( 7 \) (borrow from \( 2\) making it \( 1\)):
- \( 14 - 7 = 7 \)
- \( 1 - 8 = -7\) (so we borrow making it \(11\): \(11-8 = 3\))
- now from \(1\) becomes \(0\) as we borrowed.

Resulting:

1. \( -45.25 \) (which is obtained after full subtraction)

Thus, the result:
\[
23.45 - 68.70 = -45.25
\]

So, \( 23.45 - 68.7 = -45.25 \).