Estimation & Approximation: How To Estimate Using Given Information

Introduction

Welcome back to another Secondary 1 Math blog post on the topic of Estimation & Approximation.

In this blog post, I am going to teach you how to solve Math word problems involving square roots and cube roots of numbers.

To solve these questions, we cannot use a calculator and can only rely on the information given in the table.

Let’s Take A Look At This Estimation & Approximation Question

Some of you may already be overwhelmed by the information given in the table. Some might be asking, “Teacher, which one do I use?”

Don’t panic and just keep on reading because I will guide you through each question part.

Let’s Take A Look At Part (A)

For (a), they want us to find the square root of 580.

Look at the table and you will see that there are two choices you can refer to — or . Now, you might be wondering which is the correct one.

Let us try writing down our two options and determine which is the correct one to use.

Our first option is . What do we multiply 5.8 with to get 580? 100!

For our 2nd option, we are going to use .

We need to multiply 58 with 10 in order to get 580 so let us write that down.

Now, ask yourself — Is it easier to find the square root of 100 or the square root of 10?

If we are not allowed to use a calculator, then it will be easier to find the square root of 100!

Let us put a cross mark beside Option 2 because we will not be using it.

Now let us begin solving the question using Option 1.

Let us refer back to the table —  = 2.41. How about √100? It is 10!

Finally, you can calculate 2.41 x 10 to get 24.1.

Suggested Answer For Part (A)

24.1

Let’s Take A Look At Part (B)

Let us look back at the table above. Can you see a number similar to 38.7? It is the last column — ∛58= 3.87.

Now, in order to get 38.7, we need to multiply 3.87 by 10, so we will get this equation:

We can simplify the fraction by cancelling out the 10 in the numerator and denominator and we will be left with (3.87)³.

Some of you might be thinking that the value of (3.87)³ is not given in the table above because it only tells us the square roots and cube roots.

Don’t worry and refer back to the 4th row in the table.

Therefore, you will get 58.

Suggested Answer For Part (B)

58

Conclusion

I hope that after reading this blog post, you have gained more confidence in solving Estimation & Approximation questions that require you to refer to information in the table instead of using a calculator.

It can be overwhelming to see cube and square roots but don’t panic and remember these steps we did in this blog post:

• Look at the given options
• Decide which will help you solve the equation

Keep a lookout for more Estimation & Approximation blog posts!