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The sum of the perimeters of an equilateral triangle and a rectangle is 90 cm. Thearea, T, of the triangle and the area, R, of the rectangle, both in sq cm, satisfy therelationship R = T2 . If the sides of the rectangle are in the ratio 1: 3, then the length, in cm,of the longer side of the rectangle, is
  • a)
    24
  • b)
    27
  • c)
    21
  • d)
    18
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
The sum of the perimeters of an equilateral triangle and a rectangle i...
Let the breadth of the rectangle be b.
Length of the rectangle  3b
Let a be the side of the equilateral triangle.
Given,

Given,
2(4b) + 3a = 90
8(a2 / 4)+ 3a - 90 = 0 
⇒ 2a2 + 3a - 90 = 0
⇒ (a - 6)(2a +15) = 0
⇒ a = 6
⇒ b = 9
⇒ 3b = 27
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Most Upvoted Answer
The sum of the perimeters of an equilateral triangle and a rectangle i...
Let's assume that the equilateral triangle has side length 'a' cm and the sides of the rectangle are 'x' cm and '3x' cm.

Perimeter of the equilateral triangle:
The perimeter of an equilateral triangle is equal to the sum of the lengths of its three sides. Since all sides of an equilateral triangle are equal, the perimeter is 3 times the length of any one side.
Perimeter of the equilateral triangle = 3a cm

Perimeter of the rectangle:
The perimeter of a rectangle is equal to twice the sum of its length and width. Since the sides of the rectangle are 'x' cm and '3x' cm, the perimeter is:
Perimeter of the rectangle = 2(x + 3x) = 2(4x) = 8x cm

Given that the sum of the perimeters of the equilateral triangle and the rectangle is 90 cm, we can write the equation:
3a + 8x = 90

Area of the equilateral triangle:
The area of an equilateral triangle can be calculated using the formula: Area = (√3/4) * side^2
Area of the equilateral triangle = (√3/4) * a^2

Area of the rectangle:
The area of a rectangle is equal to the product of its length and width. Since the sides of the rectangle are 'x' cm and '3x' cm, the area is:
Area of the rectangle = x * 3x = 3x^2

Given that the area of the rectangle is the square of the area of the equilateral triangle, we can write the equation:
3x^2 = (√3/4) * a^2
Simplifying, we get:
x^2 = (√3/12) * a^2

Solving the two equations:
We have two equations:
3a + 8x = 90
x^2 = (√3/12) * a^2

We can substitute the value of a^2 from the second equation into the first equation:
3a + 8x = 90
3a + 8(√3/12) * x^2 = 90
3a + (√3/3) * x^2 = 90
3a + (√3/3) * 3x^2 = 90
3a + (√3/3) * 3(√3/12) * a^2 = 90
3a + (√3/3) * (√3/4) * a^2 = 90
3a + (√3/3) * (√3/4) * (a^2) = 90
3a + (√3/3) * (√3/4) * a^2 = 90
3a + (√3/3) * (√3/4) * a^2 = 90
3a + (√3/3) * (√3/4) * a^2 = 90
3a + (√3/3) * (√3/4) * a^2 = 90
3a + (√3/3) * (√3/4) * a^2 = 90
3
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The sum of the perimeters of an equilateral triangle and a rectangle is 90 cm. Thearea, T, of the triangle and the area, R, of the rectangle, both in sq cm, satisfy therelationship R = T2 . If the sides of the rectangle are in the ratio 1: 3, then the length, in cm,of the longer side of the rectangle, isa)24b)27c)21d)18Correct answer is option 'B'. Can you explain this answer?
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