In the diagram below, 75% of square Z is not shaded. The ratio of the area of square X to the area of square Y is 9:4. The ratio of the area of square Y to the area of square Z is 4:1.
a) What is the ratio of the area of square X to the area of square Z?
b) Find the ratio of the unshaded area of square Y to the unshaded area of square Z. 
Solution
a)
X : Y : Z
9 : 4 : 1
X : Z
9 : 1 (Answer)
b)
Total Area
Y : Z
4 : 1
16 : 4
Unshaded Area
Y : Z
15 : 3 * (see explanatory notes below)
5 : 1 (Answer)
* Total Area (ratio) Y:Z is 4:1. 75% of Z is unshaded, hence for Z, 3 units out of 4. This means 1 unit is shaded. For Y, 16 units total less 1 unit shaded = 15 units unshaded. Hence, unshaded area is Y:Z ---- 15:3.
Friday, July 31, 2009
Singapore Chinese Girls Sch 2008 PSLE Math Prelim Q42
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