This GRE quant practice question is a Select One or More Answer correct question in geometry. Concept Tested: Area of circle, right triangle, square, rectangle, parallelogram, and rhombus.
If the question does not specify how many answer choices to select, select all that apply.
If the question specifies how many answer choices to select, select exactly that number of choices.
Question 4 : The area for which of the following will necessarily be more than 50 square units.
Indicate all such expressions
Circumference of a circle = 2 π r, where r is the radius of the circle.
2 π r = 22; Take π = \\frac{22}{7})
→ r = 22 × \\frac{7}{22}) × \\frac{1}{2}) = 3.5 units
Area of a circle = π × r2 (Take π = \\frac{22}{7}) and radius = 3.5)
Area = \\frac{22}{7}) × (3.5)2 = \\frac{22}{7}) × 3.5 × 3.5 = 11 × 3.5 = 38.5 square units
Choice A is NOT one of the answers.
Area of the parallelogram = a × b × Sin θ,
where 'a' and 'b' are the measures of the adjacent sides of the parallelogram and θ is the angle between these two adjacent sides.
Area of this parallelogram = 20 × 10 × Sin θ, where 0° < θ < 180°
If we find one instance in which the area is less than 50 sq. units, it is enough to rule out this choice.
As 0° < θ < 180°, 0 < Sin θ ≤ 1
For instance, for some θ between 0° and 180°, Sin θ will be 0.1. (When θ = 5.73°, sin θ = 0.1)
The area for that parallelogram = 20 × 10 × 0.1 = 20 square units.
Choice B is NOT one of the answers.
All sides of a rhombus are equal in length.
Perimeter of rhombus = 4a = 52 → Side of a rhombus, a = 13 units
Area of a rhombus = a2 Sin θ, where 'a' is the side of the rhombus and θ is the angle between any two adjacent sides of the rhombus.
Area of the rhombus = 132 × Sin θ , where 0° < θ < 180°
As 0° < θ < 180°, 0 < Sin θ ≤ 1
For instance, for some θ between 0° and 180°, Sin θ will be 0.1.
For such a rhombus, the area = 13 × 13 × 0.1 = 16.9.
Choice C is NOT one of the answers.
Perimeter of a rectangle = 2(l + b)
2(l + b) = 50
(l + b) = 25
If we find one instance in which the area is less than 50 sq. units, it is enough to rule out this choice.
Let l = 24 and b = 1
Area of this rectangle = l × b = 24 × 1 = 24 square units
Choice D is NOT one of the answers.
Perimeter of a square = 4a, where a is the side of the square.
4a = 32 or a = 8 units
Area of a square = a2 = 82
Area of a square = 64 square units
The value of area exceeds 50 square units.
Choice E is one of the answers.
As the hypotenuse is 17, the triangle could be 15, 8, 17 right triangle. (It is a Pythagorean Triplet)
The area of 15, 8, 17 right triangle is 60 sq units.
Let’s see whether we can find a different right triangle whose hypotenuse is 17 units and area is less than 50 sq units.
Conditions to be satisfied
1. Hypotenuse 17; let the other two sides of triangle be a and b.
2. Hypotenuse 17; let the other two sides of triangle be a and b.
3. Satisfy Pythagoras Theorem: a2 + b2 = 172 → a2 + b2 = 289
The greater the difference between 'a' and 'b', smaller the area.
Let a2 = 285 and b2 = 4.
So, a = 16.88 and b = 2.
For 16.88, 2, 17 right triangle, a + b > 17.
So, the basic condition for 3-line segments to form sides of a triangle is satisfied.
The area of the triangle = \\frac{1}{2}) × b × h = \\frac{1}{2}) × 16.88 × 2 = 16.88 sq units.
Choice F is NOT one of the answers.
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