Measurement and Estimation
Another tricky concept for children is the idea of measurement, When you measure something, you relate its size to a standard unit. A 3-foot yardstick is longer than a 12-inch ruler, even though 12 is bigger than 3. At first, children may use words like “inches” or “pounds” to describe how big something is, without recognizing that these are units of length and weight. When they measure the length of a table with a tape measure, they may not understand that they tire supposed to start at one end and stretch the tape in a straight line until it reaches the other end. Children need lots of experiences with measuring and estimating size in various ways before they can really understand these concepts.