Sal discusses the conditions of matrix dimensions for which addition or multiplication are defined. Created by Sal Khan.

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

This short video and interactive assessment activity is designed to teach fifth graders about dividing 2 digits by 2 digits with a remainder.

This short video and interactive assessment activity is designed to teach fourth graders about dividing 2 digits by 2 digits with a remainder.

This short video and interactive assessment activity is designed to teach fourth graders about the relationship between dividend, divisor and quotient.

This short video and interactive assessment activity is designed to teach fourth graders about estimating the number needed using remainders.

This short video and interactive assessment activity is designed to teach fourth graders about finding the missing number.

This short video and interactive assessment activity is designed to teach fifth graders about dividing 2-digit numbers by 2-digit numbers.

This short video and interactive assessment activity is designed to teach fourth graders about dividing by 8.

This short video and interactive assessment activity is designed to teach fifth graders about dividing by 9.

This short video and interactive assessment activity is designed to teach fourth graders about number patterns based on the multiplication table.

This short video and interactive assessment activity is designed to teach fourth graders about dividing to find the time.

Demonstrates the role of parentheses in a written expression by solving one with and without the parentheses. [2:06]

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

This short video and interactive assessment activity is designed to teach second graders about expressing multiplication sentences.

This short video and interactive assessment activity is designed to teach third graders about completing the number patterns based on the multiplication table.

This short video and interactive assessment activity is designed to teach fourth graders about completing the number patterns based on the multiplication table.

Do you know how long it takes your heart to beat 100 times? Test your estimation and number sense skills with this problem-solving challenge. A one-page activity taken from the NCTM Math Challenges for Families Collection. Hints and real-world applications included.

If you like tackling formulas, then this math challenge is for you. See if you can calculate Helix's BMI (body mass index) and find out if his health is at risk. A one page NCTM Math Challenges for Families activity that engages learners in real-world skills.

This short video and interactive assessment activity is designed to teach third graders about filling in the missing number to balance the equation.

This short video and interactive assessment activity is designed to teach fourth graders about finding the adjusted rate - word problems.

This short video and interactive assessment activity is designed to teach fourth graders about finding the expression not matching a given number.