PSLE In Figure 1, ABCD is a rectangular piece of paper. After 4 identical triangles are cut out from the paper, the remaining paper is shown in Figure 2. The area of the remaining paper is 400 cm
2.
- What is the area of each triangle that was cut out?
- The perimeter of Figure 2 is 64 cm longer than the perimeter of Figure 1. What is the perimeter of each triangle?
(a)
Area of Rectangle ABCD
= 30 x 16
= 480 cm
2 Area of the 4 triangles
= 480 - 400
= 80 cm
2 Area of each triangle that was cut out
= 80 ÷ 4
= 20 cm
2 (b)
Perimeter of Rectangle ABCD
= 2(30 + 16)
= 2 x 46
= 92 cm
Perimeter of Figure 2
= 92 + 64
= 156 cm
Sum of the lengths of all the jagged edges
= 156 - (2 x 30)
= 156 - 60
= 96 cm
Sum of the lengths of the jagged edges of 1 triangle
= 96 ÷ 4
= 24 cm
Base of each triangle
= 16 ÷ 2
= 8 cm
Perimeter of each triangle
= 24 + 8
= 32 cm
Answer(s): (a) 20 cm
2; (b) 32 cm