Rachel has a square piece of paper ZABC of side 28 m. She cut along the dotted lines shown in Figure 1 to get one small square of area 16 m
2 and 8 identical right-angled triangles. Triangle DEF in Figure 2 is one such triangle. Find the length of DF.
Area of the square piece of paper
= 28 x 28
= 784 m
2 Area of 8 triangles
= 784 - 16
= 768 m
2Area of 4 outer triangles
= 768 ÷ 2
= 384 m
2 Area of the inner dotted-line square
= 784 - 384
= 400 m
2 Length of inner dotted-line square
= √400
= 20 m
Length of DF = 20 m
Answer(s): 20 m