Add and Subtract with Numbers in Standard Form

Differentiated Learning Objectives

All students to use the column method to add numbers written in the form A x 10ⁿ where n is greater than 1.
Most students use the column method to add numbers A x 10ⁿ, where n is an integer.
Some students use non-calculator methods to solve addition and subtraction problems involving standard form.

Starter/Introduction

When I teach how to add and subtract numbers in standard form, I use the starter activity to ensure students know how to convert ordinary and scientific numbers.

Prompts / Questions to consider

How can the numbers be written in ordinary form?
How can the numbers be written in standard form?
Could a place value table be helpful?
How is 10^-2 different from 10²?

Add and Subtract with Numbers in Standard Form

Click here to view the video.

There are two methods students can use to add and subtract numbers in standard form. The first method is to write the numbers using the same power of ten. The second method is to convert the numbers to decimal form.

Consider 2.4 x 10⁵ + 1.68 x 10²

Prompts / Questions to consider

How can the numbers be written with the same power of ten?
How can the numbers be converted to decimal form?
Which method is easier for addition or subtraction?
How can we use estimations or calculators to check our answers?

Plenary

I leave about 12 minutes for the plenary. I like this question because it challenges students to combine addition and subtraction within a real-life context. For an additional challenge, I provide the approximate populations of each continent so students can calculate population densities.

Prompts / Questions to consider

What is the total area of the three largest continents?
Is the question asking you to find the individual area of the remaining four continents or their total?

Differentiation

More able students could work with negative powers of ten and use approximations of one significant figure to check their solutions. Less able students could focus on the addition of large numbers using a single method.