RE: What is the answer of this math question ii) ?

[shagor21]

Dear all,
Help is needed to understand how to do this math question ii) ?

Thanks very much in advance for your time and answer.

Best regards.
Shagor21

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[svg123]

You have numbers on one of the diagnonals (15+5+12+2), which adds up to 34. You then know that every row and column plus diagnonal should add up to 34.
This is what I end up with:

14 11 7 2
1 8 12 13
4 5 9 16
15 10 6 3

[ConcernedDad]

The key I would think is to find the answer without having to complete the magic square.

Let us call the funny symbol as X (the answer we need to find).

One can see that the first column (which has X) and the third row share a common cell. Let us call it C.

In which case, the sum of first column is = 14 + X + C + 15 = 29 + X + C

Sum of the third row is = C + 5 + 9 + 16 = 30 + C

As it is a magic square, the sum of first column and third row need to be equal to each other i.e.

29 + X + C = 30 + C

X is therefore equal to 1

[Reading Mum]

I just did:

sum the diagonal that is fully populated to get 34

then fill in the missing value below the smiley by summing the 3rd row:

34- (5+9+16) = 4

then find the smiley by summing down its column:

34- (14+4+15) = 1