D

data table

A tool used to keep track of information or variables.

pages 2, 4, 5, 9, 10, 12, 22, 114, 211–212, 283, 297, 354, 359–361

decagon

A polygon with ten sides.

decimal

A number written using the base-ten place value system and containing a decimal point.
(See also decimal fraction.)

decimal fraction

A fraction written as a decimal. For example, 0.75 and 0.4 are decimal fractions and and are called common fractions.
(See also fraction and common fraction.)

denominator

The number below the line in a fraction. The denominator tells how many equal pieces the whole is divided into. For example, 4 is the denominator in the fraction .
(See also numerator.)

pages 258, 261–263

density

The ratio of an object's mass to its volume.

dependent variable

The variable whose value results from the experiment. Experimenters find the values of the dependent variable by doing the experiment. The dependent variable is often called the responding variable.

difference

The answer to a subtraction problem.

pages 46, 166

digit

The whole numbers from 0 to 9.

pages 84, 130, 133–134, 142, 161, 239

displacement

A way of measuring the volume of an object by measuring the amount of water (or some other fluid) it displaces.

pages 408–410

dissection

Cutting or decomposing a geometric shape into smaller shapes that cover it exactly.

distributive property

The distributive property says you can multiply by a sum by multiplying by each addend separately and then adding the products together. For example, to solve 5 × 8 you can partition the 8 into 6 + 2. 5 × 6 + 5 × 2 = 30 + 10 or 40.

division

The operation of making equal groups. For example, there are 3 groups of 5 in 15.

pages 66–68, 207–209, 289, 373–376