The ratio of the lengths of 2 equilateral triangles is 4:9; what is the ratio of their areas.SOMEONE PLEASE HELP D=

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embizze's profile pic

embizze | High School Teacher | (Level 1) Educator Emeritus

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If the scale factor for two similar figures, in this case equilateral triangles, is 4:9 then the ratio of the areas is the square of the scale factor; here 16:81.

Example: If the radius of an equilateral triangle is 4, then the apothem has length 2 and the sides have length `4sqrt(3)` . Thus the area of this triangle is `1/2 a p=1/2(2)(12sqrt(3))=12sqrt(3)`

If the radius of the other triangle is 9 (thus resulting in a scale factor of 4:9) then the apothem is 4.5, and the length of the sides is `9sqrt(3)` . Thus the area of this triangle is `1/2(9/2)(27sqrt(3))=243/4 sqrt(3)` .

The ratios of their areas is `(12sqrt(3))/(243/4 sqrt(3))=48/243=16/81` or 16:81 as required.

Sources:
najm1947's profile pic

najm1947 | Elementary School Teacher | (Level 1) Valedictorian

Posted on

Rules of length area and volume are simple for similar objects. If the ratio of lengths is a:b, then the ratio of areas is a^2:b^2 and ratios of their volumes is a^3:b^3.

Here if the ratio of lengths is 4:9

Hence ratios of their areas is equal to 4^2:9^2 or 16:81

The ratio of the lengths of 2 equilateral triangles is 4:9 therefore the ratio of their areas is 16:81.

Had these been similar tetrahedrons, then the ratios of their volumes would have been 4^3:9^3 or 64:729.

elekzy's profile pic

elekzy | Student, Grade 11 | (Level 1) Valedictorian

Posted on

Is a circle in or about the triangles?

najm1947's profile pic

najm1947 | Elementary School Teacher | (Level 1) Valedictorian

Posted on

The question is not understandable. Please rephrase the question.

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