Chapter SR1, Problem 25P

Solution

To perform the indicated operation in the expression $5\left(-3\right)$ .

  $-15$

Given:

The expression, $5\left(-3\right)$ .

Concept Used:

Rules of Addition/ Subtraction:

• Two numbers with similar sign always get added and the resulting number will carry the similar sign.
• Two numbers with opposite signs always get subtracted and the resulting number will carry the sign of larger number.

Rules of Multiplication/ Division:

• The product/quotient of two similar sign numbers is always positive.
• The product/quotient of two numbers with opposite signs is always negative.

Calculation:

In order to simplify the given expression $5\left(-3\right)$ , note that the sign of both numbers is different, so multiply the numbers and put a negative sign with the final result as shown below

  $\begin{array}{c}5\left(-3\right)=-\left(5\cdot 3\right)\\ =-15\end{array}$

Thus, the simplified expression is $-15$ .