To teach front end estimation to elementary math students, review how to isolate the first digit of a number, provide practice in rounding the first digit, and check students' understanding of how to complete the required operation. Use a combination of group tasks and individual work to accomplish these goals.
Keeping in mind the overall objective of developing students' ability to use front end estimation, address each sub-objective in a clear and thorough manner. First, write some large numbers on the board, and call on various students to identify the first digit of each number.
Secondly, divide students into teams. Give each team a stack of cards with a number on one side and the rounded number on the other side. Each team member takes a card, rounds the first digit of the number, changes all the other digits to zeros, and checks their rounded number with the answer on the back of the card. The team that finishes all their cards first wins.
Thirdly, assign a worksheet with a variety of front end estimation problems, including addition, subtraction, multiplication and division problems. Remind students to round first and then perform the correct operation. SoftSchools.com provides worksheets, as of 2015