# Number and Algebra In this section of the syllabus, we have topics about the number systems and notation that we use to describe the world around us, the notions of accuracy, estimation and percentage error and sequences which cross over with the  Functions and Modelling section.

Please find links to key chapters from this area of the course below. In addition, here is a growing collection of practice questions for you to use as a review exercise for the whole unit. Currently there are 5 exam style questions worth 38 marks and should be completed in about 40 minutes, before looking at the solutions.

### How do you round to 3 significant figures?

In this IB course, we are most often expected to round our answers to three significant figures. Learn how here

### What is percentage error?

There is a big difference between percentage error and absolute error - it can tell us a lot more about the world! Find out how to calculate it here

### How do you write in standard form?

Standard form is used to express very large or very small numbers, and it is important that we can work out what it means and calculate with it. Practice these skills here

### What is an arithmetic sequence?

An arithmetic sequence is one which changes in a linear fashion. It exists in plenty of real life situations and we can use our understanding of it to solve many problems!  Find out more here

### How do you know if a sequence is geometric?

A sequence is geometric if it has a common ratio between terms. They are find frequently when looking at financial situations and many more!  Learn all about them here

• ### 1.1 Standard Index Form

This is a small sup-topic to introduce or recap numbers in standard form. We will learn how to convert between numbers in standard form and base form, alongside learning how to operate with this succinct and helpful way to express numbers.

• ### 1.2 Arithmetic Sequences

These are sequences where the difference from one term to the next remains constant, like the one in the title! Arithmetic sequences crop up in all sorts of places and this unit looks at understanding how to generalise, sum and solve problems...

• ### 1.3 Geometric Sequences

These are sequences where you go from term to term by multiplying by a common ratio. The one in the title has a common ratio of 3 because each term is 3 times bigger than the previous one. Geometric sequences grow exponentially and should be...

• ### 1.6 Accuracy and Estimation

Accuracy and Estimation 1.6 When numbers are reported in the news, or as statistical results, they are either displayed exactly, or they are rounded to a certain degree of accuracy. Understanding how and when to do this can give us a deeper...

• ### Prior Knowledge - Sets of Numbers

This sub topic is about the 4 key sets of numbers that define our number system. Natural numbers, Integers, Rational numbers and Real numbers. This section starts by taking you through the concept of number sets, starting with sets that we...