F

fact family

Four related facts: two addition and two subtraction number sentences made using the same three numbers. For example, using 3, 4, and 7 the fact family is: 3 + 4 = 7; 4 + 3 = 7; 7 − 3 = 4; 7 − 4 = 3.

fair share

Splitting into equal groups or parts. For example, if there are 2 children and 7 cookies, each child's "fair share" is 3 and one-half cookies. (See also divide.)

false number sentence

A number sentence in which the numbers on both sides of the equal sign do not have the same value. For example, 3 + 4 = 3 + 2 is a false number sentence.

Fewest Pieces Rule

Using the least number of base-ten pieces to represent a number. (See also base-ten pieces.)

fixed variable

The variable in an experiment that does not change and keeps everything "fair." They are also called controlled variables.

flat

One of the base-ten pieces that is often used to represent 100. The block is made up of 100 bits. (See also base-ten pieces, bit, skinny, and pack.)

foot

A unit of length. One foot is equal to 12 inches. There are 3 feet in a yard. The plural of foot is feet. (See also inch and ruler.)

fourths

Four parts of a whole that are the same size. (See also fair share and one-fourth.)

fraction

Part of a whole in which all parts are equal or "fair shares." For example, the fraction is one of 4 equal parts. (See also fair share.)

friendly numbers

Numbers that are easy to calculate to help find a reasonable estimate. In the examples, friendly numbers are used to estimate a sum or difference. (See also benchmark numbers.)