PSLE The figure is made up of three rectangles. A straight line drawn across the rectangles, divides the figure into two parts: shaded and unshaded.
- The perimeter of the shaded part is 8 cm longer than the perimeter of the unshaded part. What is the length of kl?
- What is the area of the shaded part?
(a)
Both shaded and unshaded parts share the same slanted line. The vertical lengths of the shaded and the unshaded parts are equally long.
For the horizontal lengths, the shaded part is 8 cm longer than the unshaded part.
Horizontal lengths of shaded part
= kl + 1 u + 1 u
= kl + 2 u
Horizontal length of unshaded part = kl
2 u = 8
1 u = 8 ÷ 2 = 4
Length of kl
= 5 + 6 + 9 - 4
= 16 cm
(b)
Length of Rectangle A
= 5 + 6 + 9
= 20 cm
Area of Rectangle A
= 20 x 12
= 240 cm
2 Length of Rectangle B
= 5 + 6
= 11 cm
Area of Rectangle B
= 11 x 7
= 77 cm
2 Area of Rectangle C
= 5 x 4
= 20 cm
2
Height of the unshaded triangle
= 12 + 7 + 4
= 23 cm
Area of the unshaded triangle
=
12 x 16 x 23
= 184 cm
2
Area of the shaded part
= 240 + 77 + 20 - 184
= 153 cm
2 Answer(s): (a) 16 cm; (b) 153 cm
2