PSLE In Figure 1, RSTU 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 372 cm
2.
- What is the area of each triangle that was cut out?
- The perimeter of Figure 2 is 36 cm longer than the perimeter of Figure 1. What is the perimeter of each triangle?
(a)
Area of Rectangle RSTU
= 38 x 12
= 456 cm
2 Area of the 6 triangles
= 456 - 372
= 84 cm
2 Area of each triangle that was cut out
= 84 ÷ 6
= 14 cm
2 (b)
Perimeter of Rectangle RSTU
= 2(38 + 12)
= 2 x 50
= 100 cm
Perimeter of Figure 2
= 100 + 36
= 136 cm
Sum of the lengths of all the jagged edges
= 136 - (2 x 38)
= 136 - 76
= 60 cm
Sum of the lengths of the jagged edges of 1 triangle
= 60 ÷ 6
= 10 cm
Base of each triangle
= 12 ÷ 3
= 4 cm
Perimeter of each triangle
= 10 + 4
= 14 cm
Answer(s): (a) 14 cm
2; (b) 14 cm