F

fact family

Related math facts, e.g., 3 × 4 = 12, 4 × 3 = 12, 12 ÷ 3 = 4, 12 ÷ 4 = 3.

pages 55–57

factors

The numbers that are multiplied together to get a new number. In the problem 3 × 4 = 12, 3 and 4 are factors of 12.

pages 54, 65, 96, 112, 137, 407, 422–427, 442–445

factor tree

A diagram that shows the prime factorization of a number.

pages 443, 445

fixed variable

A variable in an experiment that is held constant or not changed.

pages 231, 351

formula

A number sentence that gives a general rule. A formula for finding the area of a rectangle is Area = length × width, or A = l × w.

pages 331, 434–437, 439–441, 556–557

fraction

A number that is a part of a whole that can be written where a and b are whole numbers and b is not zero. For example, , 0.5, and 2 are all fractions since 0.5 can be written as and 2 can be written as . Numbers like and are also fractions.

pages 58–63, 64–68, 69–73, 74–75, 76–79, 80–81, 82–85, 86–88, 89–99, 100–104, 105–118, 210–215, 216–220, 238–239, 362–367, 458–459, 460–465, 466–469, 479, 480–497, 498–502, 503–507, 508–514, 515–516, 518–525

function (machine, table)

A rule that assigns to every input number exactly one output number.

pages 399, 473, 478, 497, 507, 513