Measurement and Data
What you must understand
This domain covers unit conversion within a single measurement system (kilometers to meters, hours to minutes, liters to milliliters, kilograms to grams), area and perimeter of rectangles, line plots with fractional data, and angle measurement. You should know that a rectangle's area equals length times width and its perimeter equals twice the sum of length and width. For line plots, you interpret data in fractions of a unit and solve problems about totals and differences.
Traps to watch
- Wrong direction in conversion. A larger unit becomes a larger number of smaller units: 3 meters is 300 centimeters, not 0.03.
- Mixing area and perimeter. Area is measured in square units; perimeter in linear units. A question asking for fencing wants perimeter, not area.
- Missing side lengths. If area and one side are known, divide to find the other side before computing perimeter.
- Line-plot scales. Read the scale carefully; each mark may represent 1/4, not 1.
Rule of thumb
Convert to a common unit before adding or comparing measurements, and label every answer with its unit. For rectangle problems, ask: "Am I covering the inside (area) or going around the edge (perimeter)?"
Worked example
A rectangular garden is 7 meters long and 4 meters wide. Find its area and perimeter. Area: 7 x 4 = 28 square meters. Perimeter: 2 x (7 + 4) = 2 x 11 = 22 meters. If a fence costs 3 dollars per meter, the fencing cost is 22 x 3 = 66 dollars, because fencing follows the perimeter.