WAEC - Mathematics (2008 - No. 25)
What is the length of an edge of a cube whose total surface area is X cm2 and whose total surface area is \(\frac{X}{2}\)cm3?
3
6
9
12
설명
Total surface area of cube = 6s2
6s2 = x
s2 = x = \(\frac{x}{6}\).....(1)
volume of a cube = s2 = \(\frac{x}{2}\)
s2 = \(\frac{x}{2}\)......(2)
put(1) into (2)
s(\(\frac{x}{6}\)) = \(\frac{x}{2}\)
s = \(\frac{x}{2} \times \frac{6}{x}\)
= 3cm
6s2 = x
s2 = x = \(\frac{x}{6}\).....(1)
volume of a cube = s2 = \(\frac{x}{2}\)
s2 = \(\frac{x}{2}\)......(2)
put(1) into (2)
s(\(\frac{x}{6}\)) = \(\frac{x}{2}\)
s = \(\frac{x}{2} \times \frac{6}{x}\)
= 3cm