Chapter 1.5, Problem 43E

To determine

To calculate : The sum of the given expression:

  $2172+(-4087)$

Answer to Problem 43E

  $\text{The sum of the given expression is -1915}\text{.}$

Explanation of Solution

Given information :

Consider the expression provided in the question:

  $2172+(-4087)$

Calculation :

Evaluating the expression,

One integer is positive and the other is negative.

  $\left|2172\right|<\left|-4087\right|,\text{so the same sign as 4087}\text{.}$

  $\text{2172 + (-4087) = -1915}$

Estimating the sum by rounding off the integers to the nearest 10;

  $\text{2172 rounded to nearest 10 is 2170 and -4087 rounded to nearest 10 is -4090}\text{.}$

Therefore,

  $2170+(-4090)=-1920.$

One integer is positive and the other is negative.

  $\left|2170\right|<\left|-4090\right|,\text{so the same sign as 4090}\text{.}$

  $\text{-1920 is a close estimation of -1915}\text{.}$