The figure, not drawn to scale, is made up of two identical squares, Q and S and a rectangle R. The ratio of the area Q to the area of R to the area of S is 1 : 2 : 1. The ratio of the unshaded part of Q to the unshaded part of S is 2 : 3 respectively. Given that half of the area of Q is shaded and the total area of all the shaded parts is 30 cm
2, what is the area of the whole figure?
Q |
R |
S |
1x4 = 4 u |
2x4 = 8 u |
1x4 = 4 u |
Unshaded |
Shaded |
Unshaded |
Shaded |
Unshaded |
Shaded |
|
2 |
|
|
3 |
|
1x2 |
1x2 |
|
|
|
|
2 u |
2 u |
5 u |
3 u |
3 u |
1 u |
Since half of the area of Q is shaded, the other half of the area of Q is unshaded.
Unshaded part of Q : Shaded part of Q
1 : 1
The unshaded part of Q is the repeated identity.
LCM of 1 and 2 = 2
Area of Q is the combined repeated identity.
LCM of 1 and 4 = 4
Q : R : S
1 : 2 : 1
4 : 8 : 4
Shaded part of Q : Shaded part of S
2 : 3
Total shaded area
= 2 u + 1 u
= 3 u
3 u = 30
1 u = 30 ÷ 3 = 10
Area of the whole figure
= 2 u + 8 u + 3 u
= 13 u
= 13 x 10
= 130 cm
2 Answer(s): 130 m
2