options: Know that there are numbers that are not rational, and approximate them by rational numbers.

Apply and extend previous understandings of operations with fractions to add, subtract, multiply, and divide rational numbers.

Use properties of rational and irrational numbers.

Represent and model with vector quantities.

Apply and extend previous understandings of multiplication and division to divide fractions by fractions.

Extend the properties of exponents to rational exponents.

Perform operations on matrices and use matrices in applications.

Reason quantitatively and use units to solve problems.

Perform arithmetic operations with complex numbers.

Use complex numbers in polynomial identities and equations.

Perform operations on vectors.

Represent complex numbers and their operations on the complex plane.

Apply and extend previous understandings of numbers to the system of rational numbers.

Compute fluently with multi-digit numbers and find common factors and multiples.
problem_activity: Task
Nina was finding multiples of 6. She said,
18 and 42 are both multiples of 6, and when I add them, I also get a multiple of 6: $$18+42 = 60.$$
Explain to Nina why adding two multiples of 6 will always result in another multiple of 6.


correct_option_index: 13