6
$\begingroup$

The following question was asked in a mock test for which I am preparing and I was unable to solve it.

enter image description here

What is the missing number? It must be one of these answers:

A -19
B -5
C 9
D -9

The pattern I saw was that each block is the sum of the two directly below it, divided by two. For example, 5 (the top number) = (8 + 2) / 2. Using this pattern I got -1 as the answer but it's not an option and I am unable to see any other pattern.

So, can someone please tell me how should I attempt the question?

Improve this question
$\endgroup$
1
  • $\begingroup$ Perhaps you mistakenly used +5 instead of -5 in the last block of the third row, when calculating your provisional answer of -1? $\endgroup$
    – Greg Martin
    Nov 16, 2020 at 8:52

3 Answers 3

Reset to default
3
$\begingroup$

The answer should be

A -19

Because

If you add two adjacent blocks and divide by 2 you get the number of the block on top of/above them

F ex. 8+2=10 ----> 10/2=5

Improve this answer
$\endgroup$
2
  • 1
    $\begingroup$ Looks like we both spotted this within moments of each other! $\endgroup$
    – Stiv
    Nov 15, 2020 at 13:08
  • 1
    $\begingroup$ we did, but I think you're right with the "trick" $\endgroup$
    – Prim3numbah
    Nov 15, 2020 at 13:18
12
$\begingroup$

If the dividing line between the '9' and '?' cells is actually supposed to be positioned more to the right, then the answer is:

A) -19

Because:

The number above each pair of two adjacent cells is their arithmetical average (i.e. the mean) - e.g. for the top two rows, 5 is the average of 8 and 2.

In this case, the average of 9 and -19 yields -5 (the cell above them), as required.

However, if this is intended as a trick question and the solver is supposed to note that the -5 cell is only above a single box, then:

that box should contain the answer B) -5, as the average of one value is that value itself...!

It really depends on whether that line is positioned correctly or if it is intended as a trick question.

Improve this answer
$\endgroup$
1
  • $\begingroup$ nice, deja vu :) $\endgroup$
    – Prim3numbah
    Nov 15, 2020 at 13:07
0
$\begingroup$

I think the answer is...

A(-19)

Because...

I made a drawing so that it is clearer: enter image description here The three blocks(like in the drawing) that contain the block with the question mark is outlined in red: enter image description here In this case, $a=-5$, $b=9$, and $c$ is the one represented with the question mark. Therefore, $c=2a-b=-10-9=-19$. Hence, the answer is -19(option A)

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.