The figure, not drawn to scale, is made up of two identical squares, J and L and a rectangle K. The ratio of the area J to the area of K to the area of L is 1 : 2 : 1. The ratio of the unshaded part of J to the unshaded part of L is 3 : 5 respectively. Given that half of the area of J is shaded and the total area of all the shaded parts is 60 cm
2, what is the area of the whole figure?
J |
K |
L |
1x6 = 6 u |
2x6 = 12 u |
1x6 = 6 u |
Unshaded |
Shaded |
Unshaded |
Shaded |
Unshaded |
Shaded |
|
3 |
|
|
5 |
|
1x3 |
1x3 |
|
|
|
|
3 u |
3 u |
8 u |
4 u |
5 u |
1 u |
Since half of the area of J is shaded, the other half of the area of J is unshaded.
Unshaded part of J : Shaded part of J
1 : 1
The unshaded part of J is the repeated identity.
LCM of 1 and 3 = 3
Area of J is the combined repeated identity.
LCM of 1 and 6 = 6
J : K : L
1 : 2 : 1
6 : 12 : 6
Shaded part of J : Shaded part of L
3 : 5
Total shaded area
= 3 u + 1 u
= 4 u
4 u = 60
1 u = 60 ÷ 4 = 15
Area of the whole figure
= 3 u + 12 u + 5 u
= 20 u
= 20 x 15
= 300 cm
2 Answer(s): 300 m
2