PSLE In Figure 1, CDEF 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 240 cm
2.
- What is the area of each triangle that was cut out?
- The perimeter of Figure 2 is 52 cm longer than the perimeter of Figure 1. What is the perimeter of each triangle?
(a)
Area of Rectangle CDEF
= 27 x 10
= 270 cm
2 Area of the 4 triangles
= 270 - 240
= 30 cm
2 Area of each triangle that was cut out
= 30 ÷ 4
= 7.5 cm
2 (b)
Perimeter of Rectangle CDEF
= 2(27 + 10)
= 2 x 37
= 74 cm
Perimeter of Figure 2
= 74 + 52
= 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 ÷ 4
= 18 cm
Base of each triangle
= 10 ÷ 2
= 5 cm
Perimeter of each triangle
= 18 + 5
= 23 cm
Answer(s): (a) 7.5 cm
2; (b) 23 cm