11 Plus Exams Forum

Ok so all members of family have had a go at this but just can't do it!!

2 [24] 36 3 [36] 48

5 [?] 72

Find the missing number!!!

60?

2x12=24
24+12=36
3x12=36
36+12=48

Then
5x12=60
60+12=72

Of course this may all be rubbish

Not rubbish at all Doodles! Well done in fact.
Tagore

Strangely if you just take 12 from the number on the right you get the same
answer

2 [24] 36 3 [36] 48

5 [?] 72

Find the missing number!!!

I believe you need to use the outside numbers to arrive at the middle number so:

(2 x 36) / (2 + 1) = 24
(3 x 48) / (3 + 1) = 36
(5 X 72) / (5 + 1) = 60

I'm reading these forums with interest to see what sort of things get asked in these tests, and I've never come across these types of problems before.

If the three numbers can be termed A and C

I take it that what the kid needs to do is (in a roundabout way) generate a method for caluclating B that uses A and C using +, -, / and x and any constants they require?

Thus for the question above we have

2 [24] 36
3 [36] 48 and
5 [x] 72

I presume they have to show working too?

Would it be ok to show it as:

b=((A+1)x12)-12

Sorry, I'm new to this!

Len Scap wrote:I presume they have to show working too?

No - just the answer

Would it be ok to show it as:
b=((A+1)x12)-12

You don't need to show how you got there - but you should be looking for an answer that uses both A and C

Hi, no they just have to mark the right box. Of course they have to be able to work out the answer in order to that so they do need to be familiar with the question type and able to look at numbers logically. Lots of practice ahead of time will help.

Okanagan wrote:

Len Scap wrote:I presume they have to show working too?

No - just the answer

Would it be ok to show it as:
b=((A+1)x12)-12

You don't need to show how you got there - but you should be looking for an answer that uses both A and C

Ok - thanks.

I actually ended up with two equations:

c=(a+1)x12 and
b = c-12

I just substituted to get to b=((a+1)x12)-12, but I used a and c to get there.