PSLE In Figure 1, EFGH is a rectangular piece of paper. After 6 identical triangles are cut out from the paper, the remaining paper is shown in Figure 2. The area of the remaining paper is 315 cm
2.
- What is the area of each triangle that was cut out?
- The perimeter of Figure 2 is 42 cm longer than the perimeter of Figure 1. What is the perimeter of each triangle?
(a)
Area of Rectangle EFGH
= 27 x 15
= 405 cm
2 Area of the 6 triangles
= 405 - 315
= 90 cm
2 Area of each triangle that was cut out
= 90 ÷ 6
= 15 cm
2 (b)
Perimeter of Rectangle EFGH
= 2(27 + 15)
= 2 x 42
= 84 cm
Perimeter of Figure 2
= 84 + 42
= 126 cm
Sum of the lengths of all the jagged edges
= 126 - (2 x 27)
= 126 - 54
= 72 cm
Sum of the lengths of the jagged edges of 1 triangle
= 72 ÷ 6
= 12 cm
Base of each triangle
= 15 ÷ 3
= 5 cm
Perimeter of each triangle
= 12 + 5
= 17 cm
Answer(s): (a) 15 cm
2; (b) 17 cm