Let x be the length of the edge of the original cube. When increased to twice its original size it becomes 2 x which gives a volume of
2x × 2x × 2x = 8x³
The volume is known. Hence
8x³ = 64,000
x³ = 8,000 which gives x = 20
The area of one face of the original (before the increase) is given by x2
x² = 20² = 400 square centimeters
