Answer:
D. 24
Step-by-step explanation:
Let's name the diagram
Row 1: a1, a2, a3
Row 2: b1, b2, b3
Row 3: c1, c2, c3
From the diagram,
b2 and c2 have been given
All rows, columns and diagonal must sum up to 18
If b2=6 and c2=4
a2=18-(6+4)
=18-10
=8
a2=8
Assume a1=4
Diagonals a1+b3+c3=18
4+6+c3=18
10+c3=18
c3=18-10
=8
Assume a3=6
Diagonals a3+b2+c1=18
6+6+c1=18
12+c1=18
c1=18-12
=6
So b1=18-(6+4)
=18-10
=8
b1=8
b3=18-(6+8)
=18-14
=4
b3=4
Input all the numbers into the boxes
We have,
4 8 6
8 6 4
6 4 8
Corner numbers are a1,a3,c1,c3
=4,6,6,8
Sum of all the corner numbers=4+6+6+8
=24
D. 24
