NL Grade 3 Math cheat sheet

Place value: In a 3-digit number, the digits represent hundreds, tens, and ones. Example: 472 = 4 hundreds + 7 tens + 2 ones.

Comparing numbers: Compare hundreds first, then tens, then ones. The number with the greater digit in the first different place is larger.

Rounding to nearest ten: Look at the ones digit. If it is 5 or more, round up; if less than 5, round down. Example: 47 rounds to 50.

Addition and subtraction: Line up digits by place value. Regroup when a column sum is 10 or more, or when subtracting a larger digit from a smaller one.

Multiplication: Multiplication is repeated addition. 4 × 3 means 4 groups of 3, which equals 12.

Fractions: A fraction shows equal parts of a whole. The denominator tells how many equal parts; the numerator tells how many parts are taken. Example: 3/4 means 3 out of 4 equal parts.

Money: $1.00 = 100 cents. To add money, line up decimal points and regroup as with whole numbers.

Even and odd: Even numbers end in 0, 2, 4, 6, or 8. Odd numbers end in 1, 3, 5, 7, or 9.

Repeating patterns: A repeating pattern has a core that repeats. Example: red, blue, red, blue, ... The core is red, blue.

Growing patterns: In a growing pattern, the number of elements increases by a constant amount each time. Example: 2, 4, 6, 8, ... increases by 2.

Number sequences: To find the rule, compare consecutive terms. The rule may be add, subtract, multiply, or divide by a constant.

Input/output tables: The rule relates input to output. Example: input + 5 = output. If input is 3, output is 8.

Equality: The equals sign means "is the same as." An equation like 5 + 3 = 8 is balanced.

Missing number: In 7 + ? = 12, subtract 7 from 12 to find the missing number: 5.

Patterns in tables: Look for a consistent change in the output column as the input increases by 1.

2-D shapes: Polygons are closed shapes with straight sides. Examples: triangle (3 sides), quadrilateral (4 sides), pentagon (5 sides), hexagon (6 sides).

3-D solids: Faces are flat surfaces, edges are where faces meet, and vertices are corners. Example: A cube has 6 faces, 12 edges, and 8 vertices.

Symmetry: A line of symmetry divides a shape into two matching halves. A square has 4 lines of symmetry.

Congruent shapes: Congruent shapes have the same size and shape. They may be rotated or flipped.

Perimeter: Perimeter is the distance around a shape. Add the lengths of all sides. Example: rectangle with sides 3 cm and 5 cm has perimeter 16 cm.

Area: Area is the number of square units needed to cover a shape. For a rectangle, area = length × width.

Angles: A right angle is 90°. It looks like the corner of a square. An angle smaller than a right angle is acute; larger is obtuse.

Grid positions: Use ordered pairs (x, y) to locate points on a grid. The first number tells how far right; the second tells how far up.

Bar graphs: The height of each bar shows the number of items in that category. The scale tells what each grid line represents.

Pictographs: Each picture stands for a number of items, shown in the key. Example: key = 2 means each picture represents 2 items.

Line plots: A line plot shows data using X marks above a number line. The number of Xs above a value shows how many times that value occurs.

Mode: The mode is the number that appears most often in a data set. Example: in 2, 3, 3, 5, the mode is 3.

Range: The range is the difference between the greatest and least values. Example: for 4, 7, 9, range = 9 − 4 = 5.

Probability: Probability describes how likely an event is. It ranges from 0 (impossible) to 1 (certain).

Fair games: A game is fair if each player has the same chance of winning. If outcomes are equally likely, probability = number of favorable outcomes ÷ total number of outcomes.