Chloe and Zoe made the patterns abore using some chalk on the sidewalk by their house. One of the numbers was accidentally erased when their little brother stepped on it. Which of the following numbers should they use to replace the question mark? A. 7
B 8
C. 9
D. 6

the answer to this question is b8

Given a cube of sides 4 units with vertices: A, B, C, D, E, F, G, H such that the top square is ABCD and the bottom square is EFGH with AC, BD the diagonals of the top square and EG, FH the diagonals of EFGH.

The shape of the cross-section formed when a plane containing line AC and line EH intersects the cube is the rectangle ACEH.

We obtain the value of line AC which is equal to line EH using the pythagoras rule which states that , where c is the length of line AC, a is the length of line AB = 4 and b is the length of line BC = 4.

Thus, 


Therefore, the shape of the cross-section formed when a plane containing line AC and line EH intersects the cube is the rectangle ACEH with length of units and width of 4 units.

Area of a rectangle is given by
Area = length x width
square units.