Identify these questions

Another common type of question in numerical reasoning tests are number series that go ‘down' in value.

They’re questions that look like this:

What is the next number in this series?

4, 2, 0, ?

A 1 B 2 C -2 D -4

OR,

The numbers in each pair of brackets follow the same rule.

Find the missing number.

[16, 8] [14, 7] [?, 11] [36, 18]

A 18 B 20 C 22 D 24

A distinguishing characteristic of these types of questions is that the subsequent value is always lower than the previous number.

The strategy to answer these questions

To answer these questions, you will be required to:

1. Identify the relationship (this relationship or pattern will hold true for all the numbers) between the numbers, and,
2. Use that relationship to find the missing number or the grouped number set.

Here are rules to uncovering the pattern when the number series is going down:

• For smaller gaps between numbers, look at subtraction. Subtraction is sometimes used for larger gaps too and a giveaway would be a consistent gap (although they can decrease or increase with an additional pattern as well).
• For larger gaps between numbers, look at division.
  
• For odd gaps, where no standard subtraction or division results in a pattern, try combinations of any of addition, subtraction, multiplication and division WITH subtraction or division. But note that because the number does go down, the subtraction or division must be LARGER than the addition or multiplication.

Example Question/s

Watch video for explanation of the following question/s:

The numbers in each pair of brackets follow the same rule.

Find the missing number.

[16, 8] [14, 7] [?, 11] [36, 18]

A 18 B 20 C 22 D 24

The numbers in each pair of brackets follow the same rule.

Find the missing number.

[6, 3] [30, 6] [72, 9] [?, 10]

A 80 B 100 C 110 D 120

Key Rules to remember

A number series going down is likely to have a pattern that contains:

• Subtraction for smaller gaps between numbers – but what you’re really looking for is a consistent gap size.
• Division for larger gaps between numbers.
• A combination of any of the 4 operators combined with subtraction or division for patterns not found with subtraction or division purely.

Practice time!

Now, it's your turn to practice.

Click on the button below and start your practice questions. We recommend doing untimed mode first, and then, when you're ready, do timed mode.

Every question has two solutions videos after you complete the question. The first is a quick 60 second video that shows you how our expert answers the question quickly. The second video is a more in-depth 5-steps or less explainer video that shows you the steps to take to answer the question. It's really important that you review the second video because that's where you'll learn additional tips and tricks.

Once you're done with the practice questions, move on to the next checkpoint.

Now, let’s get started on your practice questions.

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