Which expression represents the phrase "twice the difference of a number and 5"?
2 answers:
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Answer:
128.8 cm²
Step-by-step explanation:
In the image attached below, the regular polygon is a square which is composed of a small square and a large square. In a square, all the sides are equal.
For the small square, half of the diagonal is 4 cm, therefore the length of the diagonal is 8 cm (2 × 4 cm). Let the length of the side be a cm, using Pythagoras theorem:
a² + a² = 8²
2a² = 64
a² = 32
a = √32 = 5.7 cm
The area of the small square = length × length = 5.7 × 5.7 = 32.5 cm²
For the large square, half of the diagonal is 9 cm, therefore the length of the diagonal is 18 cm (2 × 9 cm). Let the length of the side be b cm, using Pythagoras theorem:
b² + b² = 18²
2b² = 324
b² = 162
b = √162 = 12.7 cm
The area of the large square = length × length = 12.7 × 12.7 = 161.3 cm²
The area of the shaded region = Area of large square - Area of small square = 161.3 cm² - 32.5 cm² = 128.8 cm²
