Question

Use a calculator to find the sum. Estimate the sum by rounding to check that your answer is reasonable.

2172 + (– 4087)

Short answer

Answer is – 1915

Step-by-step solution

Apply the concept of adding or subtracting integers 

Rule: The sum of any integer and its opposite is equal to zero.

Explanation: Adding two positive integers always yields a positive sum; adding two negative integers always yields a negative sum. To find the sum of a positive and a negative integer, take the absolute value of each integer and then subtract these values.

Explanation: How to add or subtract the integers.

To add two numbers with the same sign, first add the two numbers ignoring the sign and then put their common sign before the answer.

To add two numbers with the opposite sign, ignore their signs and subtract the smaller number from the bigger number. Then put the sign of the bigger number before the answer.

Find the sum 2172 + (– 4087) 

To add two integers, we need to check the signs of those two integers.

Rule: If they are with the opposite sign (one is positive and other is negative), subtract the smaller number from the bigger number ignoring the sign, then put the sign of bigger number before the answer.

Here 4087 is bigger number and negative, so the answer will be negative.

Evaluate: 2172 + (– 4087) = 2172 – 4087 = – 1323

We can write: 2172 + (– 4087) = – 1323