11 Plus Exams Forum

Hi

Can someone pls help.

The numbers in these groups follow the same rule.

(2 , 3, 5) (3, 1, 2) (1, ?, 6)

Which of the following numbers best replaces the question mark?

(a) 3
(b) 5
(c) 7
(d) 8


My son marked (b) is the correct answer but the answer key shows the correct answer is (c). .

Thanks

Uma

Hi Uma

Think you multiply the first two and subtract 1. So 2 x 3 = 6, 6 -1=5 etc.

Hope this helps.

5.

take the first number way from the third

yoyo123 wrote:5.

take the first number way from the third

That wouldn't work for the middle set of numbers though.

true!

take the smaller from the bigger?

Add the outer ones and subtract 4??

EDIT: Maybe not...

Ed's mum

Why not - the logic fits

The answer key said the answer was 7. But I reckon Uma's son was right saying 5.

middle number is difference between 2 outer numbers

Dear Uma

Where have you found this question?

(2 , 3, 5) (3, 1, 2) (1, ?, 6)

I agree with Ed's mum.

The rule for these questions is that the numbers either side have been used to make the middle number. Sometimes you use one operation sometimes a second operation is required. The same rule must be used for all three sets.

2 + 5 = 7 how do you get to 3, take away 4

3 + 2 =5 , how do you get to 1, take away 4

So the rule is add the two outer numbers and then subtract 4

1+ 6 = 7 subtract 4 = 3

(2 , 3, 5) (3, 1, 2) (1, ?, 6)

You cannot say the difference between the 2 as that would be 2 different rules.

ie. right minus left followed by left minus right.

Its either 2 minus 5 and therefore 3 minus 2 or

5 minus 2 and therefore 2 minus 3.