number pattern

[Uma]

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

[pixiequeen]

Hi Uma

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

Hope this helps.

[yoyo123]

5.

take the first number way from the third

[Ed's mum]

5.

take the first number way from the third

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

[yoyo123]

true!

take the smaller from the bigger?

[Ed's mum]

Add the outer ones and subtract 4??

EDIT: Maybe not...

[999 mum]

Ed's mum

Why not - the logic fits

[hermanmunster]

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

[patricia]

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

[patricia]

(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.