Younger students can begin learning to make educated guesses when estimating how many cups of water a container can hold. It may be helpful to start with a small container and work through several sizes, each getting bigger as you go along. This will demonstrate for the children that the larger containers will hold more cups of water and help them to refine their guesses. As the activity progresses, discussing how each student is coming up with his guesses can illustrate estimation strategies.
Students can learn to estimate with decimals using a pretend store and play money. This activity calls for you to write a list of items for sale and their prices on the board, or by using a handout. Each student has a set amount of play money and can pick which items she would like to buy. The student can then use either rounding or front-end estimation. When using rounding, she rounds the prices to the nearest dollar and estimates the cost of the items to determine whether she has enough money for the purchase. When using front-end estimation, the student simply adds the first digit of each price to estimate the final cost. For higher-priced items, the child may need to use the first two digits. Each student can share with the class the strategy she used and whether the estimate was accurate.
Students can use pennies to estimate the length of standard classroom items. You can give each student a container of pennies and a list of items or have them work in groups. The children guess how many pennies long each item is and then check their estimates by lining the pennies up along the item. The students may at first be way off in their estimates, but as the activity progresses, the children will learn to make educated guesses based on previous results. After the students become comfortable using the pennies for measurement, each person can measure a penny. Then students can use the pennies to estimate the actual length of each item.
Students can guess the number of pieces of cereal that fit in a small cup and then use the pieces of cereal in estimating the volume of the cup. After making their guesses, each student can trace the bottom of the cup on a piece of paper. He makes a line vertically through the center of the circle and then horizontally. The student then measures the height of the cup and makes a line on the paper to represent that height. The children line up the pieces of cereal side by side along each line, one line at a time, and count how many pieces fit. Each answer is written down and then the three answers are multiplied. The product is the estimate of how many pieces of cereal will fit in the cup or the volume of the cup in cereal pieces.