Readily give the sums and differences of single-digit numbers in familiar contexts where the operation makes sense to them, and they can judge the reasonableness of the answer. Give rough estimates of numerical answers to problems before doing them formally. Explain to other students how they go about solving numerical problems. Make quantitative estimates of familiar lengths, weights, and time intervals and check them by measurements.
Primary students work with and observe the properties of five different kinds of wood.
They begin with a free exploration time, then go on a wood hunt to find matches for their samples, drop water on the samples, float them in basins of water, and discover a way to sink them. They test two pieces of wood to find out exactly how many paper clips it takes to sink them, and then organize their results by making a bar graph. Assemble, describe, take apart, and reassemble constructions using interlocking blocks, erector sets, and the like. Make something out of paper, cardboard, wood, plastic, metal, or existing objects that can actually be used to perform a task. Measure the length in whole units of objects having straight edges.