Activities to Teach Students to Estimate Sums and Differences of Decimals Using Benchmarks

As we progress in mathematics, we encounter decimals that require estimation to solve problems faster and more efficiently. Estimation is a valuable skill in mathematics as it enables us to approximate a value, which can be used to validate our results. Estimation can also help us to quickly evaluate whether our answer makes sense or not. In this article, we will discuss some activities to teach students to estimate sums and differences of decimals using benchmarks.

What is estimation?

To begin with, let us understand what estimation means. The process of estimation involves finding an approximate value of a given quantity. Estimation is done to get a rough idea of the answer, especially when we don’t have the exact value of the quantity. By approximating, we can gauge whether the answer is rational or not to decide whether more precision is required.

What are benchmarks?

A benchmark is a numerical amount that helps us estimate the value of a quantity. Typically, benchmarks are rounded numbers that are easy to work with and remember. These benchmarks act as reference points that provide a frame of reference when estimating the value of a quantity.

Now, let us look at some creative activities that can be used to teach students to estimate sums and differences of decimals using benchmarks.

1. Estimation Jar

An estimation jar is an excellent tool to help students develop their estimation skills. It is a jar that contains objects such as marbles, beads, and buttons. The number of objects in the jar is not disclosed, and the students have to estimate the total number of objects in the jar. This exercise can be adapted to decimals by filling the jar with decimal numbers. The students have to estimate the sum or difference of these decimals by using benchmarks.

2. Guessing Game

This activity involves having two teams compete with each other. One team provides a decimal number, and the other team has to estimate the decimal number that results from adding or subtracting it from a benchmark. They are given a time limit to estimate as many questions as possible, and the team with the most correct answers wins.

3. Calculator Race

This activity involves two students who perform a specific calculation using their calculators. The first student is given a decimal number, and the second student is given a benchmark. Both students race to see who can calculate the closest approximation of the resulting decimal number.

4. Estimation Challenge

In this challenge, students are given a set of decimals that represent the sum or difference of two decimals. The students have to estimate the values of the two decimals by using benchmarks and then add or subtract them to find the answer. This activity encourages students to estimate the sum or difference of decimals by breaking them down into smaller, easily measurable parts.

5. Shopping Spree

This activity involves having students imagine that they are going on a shopping spree at their favorite store. The students are given a budget, and they have to estimate the cost of the items they want to buy by using benchmarks. This activity helps students to estimate the sum of decimals and enables them to understand the importance of estimation in real-life situations.


Estimating the sum and difference of decimals is a valuable skill that students can use throughout their lives to make informed decisions. By teaching students to estimate decimals using benchmarks, we can help them develop their estimation skills and make better-informed decisions. Employing these activities in the classroom will not only help students understand the concept of benchmarks but will also make learning an enjoyable experience.

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