PSLE In Figure 1, GHJK is a rectangular piece of paper. After 8 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 72 cm longer than the perimeter of Figure 1. What is the perimeter of each triangle?
(a)
Area of Rectangle GHJK
= 25 x 20
= 500 cm
2 Area of the 8 triangles
= 500 - 400
= 100 cm
2 Area of each triangle that was cut out
= 100 ÷ 8
= 12.5 cm
2 (b)
Perimeter of Rectangle GHJK
= 2(25 + 20)
= 2 x 45
= 90 cm
Perimeter of Figure 2
= 90 + 72
= 162 cm
Sum of the lengths of all the jagged edges
= 162 - (2 x 25)
= 162 - 50
= 112 cm
Sum of the lengths of the jagged edges of 1 triangle
= 112 ÷ 8
= 14 cm
Base of each triangle
= 20 ÷ 4
= 5 cm
Perimeter of each triangle
= 14 + 5
= 19 cm
Answer(s): (a) 12.5 cm
2; (b) 19 cm