Measurement and Data
Measurement and Data covers time, mass and liquid volume, scaled graphs and line plots, and area and perimeter. Grade 3 items often combine measuring with arithmetic, so read the units before you calculate.
Core rules
- Tell time to the nearest minute and solve elapsed-time problems by counting forward in jumps (3.MD.A.1).
- Measure and estimate liquid volume in liters and mass in grams and kilograms (3.MD.A.2).
- A scaled picture graph or bar graph uses one symbol or interval for more than one item. Read the key first (3.MD.B.3).
- A line plot marks each measurement with an X above its value; the scale may use halves or fourths (3.MD.B.4).
- Area is the number of square units covering a flat figure. For a rectangle, area = length × width (3.MD.C.7).
- Perimeter is the distance around a figure; for a rectangle, perimeter = 2 × (length + width).
Worked example
A rectangle is 6 cm long and 4 cm wide. Area: 6 × 4 = 24 square centimeters, because the rectangle can be tiled with 6 columns of 4 unit squares. Perimeter: 6 + 4 + 6 + 4 = 20 centimeters, because perimeter adds the four side lengths. The numbers are related but not interchangeable: the area is 24 cm² and the perimeter is 20 cm.
Traps that cost marks
- Reporting area in centimeters instead of square centimeters.
- Multiplying length by width when the question asks for the distance around the edge.
- Counting symbols on a scaled graph without multiplying by the key.
- Finding elapsed time by subtracting minutes only when the times cross an hour.
- Counting X's on a line plot instead of reading their positions on the number line.