More missing value addition and subtraction problems with negative numbers | Khan Academy

TL;DR

Learn how to add and subtract positive and negative numbers through a step-by-step explanation and number line examples.

Transcript

• Let's give ourselves a little bit more practice adding and subtracting positive and negative numbers. So, let's say that we have the statement, four is equal to negative eight minus blank. Like always, I encourage you to pause the video and see if you can figure out what blank would be to make the statement true. That negative eight minus blank i... Read More

Key Insights

• #️⃣ Adding a positive number to a negative number moves the sum to the right on a number line.
• #️⃣ Subtracting a positive number from a negative number also moves the result to the right on a number line.
• #️⃣ Subtracting a negative number is the same as adding a positive number.

Questions & Answers

Q: How can we solve the equation "four is equal to negative eight minus blank"?

To solve this equation, we need to add 12 to negative eight. By adding 12, we get the equivalent statement "four is equal to negative eight minus negative 12".

Q: How do we simplify subtracting a negative?

Subtracting a negative is the same as adding a positive. So, subtracting a negative two becomes adding a positive two. Therefore, the equation "something subtracting a negative two is equal to negative seven" is equivalent to "something plus two is equal to negative seven".

Q: How can we solve the equation "negative four is equal to blank minus nine"?

To solve this equation, we need to subtract nine from positive five. By subtracting nine, we get the equivalent statement "negative four is equal to five minus nine".

Q: What is the importance of using a number line in these examples?

A number line helps visually represent the process of adding or subtracting positive and negative numbers. It allows us to see the direction and magnitude of the changes.

Summary & Key Takeaways

• The video teaches the viewer how to add and subtract positive and negative numbers using the concept of a number line.

• The first example shows how to solve the statement "four is equal to negative eight minus blank" by adding 12 to negative eight.

• The second example demonstrates how to solve the equation "something plus two is equal to negative seven" by subtracting two from negative seven.

• The third example explains how to solve the equation "negative four is equal to blank minus nine" by subtracting nine from positive five.