# Question Type 18 Method Sheet

Type 18 – Calculate the middle number from outside numbers. (Related numbers.)

In this question type you are asked to complete the mathematical sum by inserting the correct answer in the brackets. The answer will go on one side of the equal sign in order to complete the sum. We work from left to right recording our answers as we go!!

Look at this first example and then we can work our way through the question until we get the answer: -

Look at the first two groups of numbers. Each middle number has been made by using the two outside numbers.
Find the number that will complete the third group of numbers in the same way.

5  (12)  7       4  (7)  3       2  ( ? )  6

Remember the two outside numbers must be used to calculate the number in the brackets.

If we start with 5  (12)  7 we must ask ourselves how do we get 12 using 5 and 7?
If we add 5 and 7 we will get 12.

Now does the same rule apply to 4  (7)  3 ? Does adding 4 and 3 give us 7?
The answer is yes, 4 plus 3 does give us 7.

When the same rule applies to the first and second sets of brackets we then apply the same rule to the third set of brackets to get our answer.
So if we add 2 and 6 we will get 8 and this is our answer which we would then write in the bracket.

There may be one than one mathematical way to answer the same question. The important part is that you can apply the same rule to both the first and second set of brackets.

There is a huge selection of variations possible in this question type.
Some possible variations that might be used in this question type are:-

The list of variations is very large indeed.

THINGS TO LOOK OUT FOR!!!!

Make sure that you do your calculations very carefully in order to avoid simple errors.
Remember that the same rule must apply to the first and second sets of brackets before you then apply the same rule to the third set of brackets in order to get our answer.
Avoid guessing the answer – though if you are completely stuck a guess is better than a blank answer space.
There is not really any “trick” or “technique” that can be taught for this question type as it relies very strongly on the child having a good understanding of mathematical concepts and being able to use them accurately and quickly.
This question type is one of the most difficult mathematics questions that are set.
If the outside numbers are small and the middle number is very large then probably the question involves multiplication in some aspect of the calculation.
If the outside numbers are large and the middle number is small then probably the question involves division in some aspect of the calculation.
This question type is one of the most difficult mathematics questions that are set.

NB When you are completing a Verbal Reasoning test in Multiple-Choice format the correct answer will always be one of the choices that you are given on your answer sheet. If your answer does not match one of the answers that you are given then your answer is wrong.