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2 years ago

HELP PLS ITS URGENT

Mathematics

1 answer:

marysya [2.9K]2 years ago

3 0

Melanie: 15 years old

Kevin: 5 years old

Assume Kevin's present age is x.

That means that 3 years ago, his age would be x - 3.

Melanie's age would be 6(x - 3).

Same thing for 5 years into the future:

Kevin's age would be x + 5.

Melanie's age would be 2(x + 5).

The two equations we have here are:

$\left \{ {{x + 5 = 2(x + 5)} \atop {x - 3 = 6(x - 3)}} \right.$

By subtracting both equations, we are simplified to:

8 = -4x + 28

By solving the equation, we get x = 5.

That means that Kevin's current age is 5 years old.

Melanie's age could be calculated by substituting Kevins'.

6(x - 3) --> 6(5 - 3) --> 12

Since that was 3 years ago, you need to add 3 to 12 to get her current age.

12 + 3 = 15

Melanie's current age is 15 years old.

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The perimeter of equilateral triangle ABC is 81/3 centimeters, find the length of the radius and apothem.

MAXImum [283]

There is a typo error, the perimeter of equilateral triangle ABC is 81/√3 centimeters.

Answer:

Radius = OB= 27 cm

Apothem = 13.5 cm

A diagram is attached for reference.

Step-by-step explanation:

Given,

The perimeter of equilateral triangle ABC is 81/√3 centimeters.

Substituting this in the formula of perimeter of equilateral triangle = $3\times\ side$

$3\times\ side$ $=[tex]81\sqrt{3}$

$Side = \frac{81\sqrt{3} }{3} =27\sqrt{3} \ cm$

Thus from the diagram , Side $AB=BC=AC= 27\sqrt{3} \ cm$

We know each angle of an equilateral triangle is 60°.

From the diagram, OB is an angle bisector.

Thus $\angle OBC = 30$ °

Apothem is the line segment from the mid point of any side to the center the equilateral triangle.

Therefore considering ΔOBE, and applying tan function.

$tan\theta =\frac{perpendicular}{base} \\tan\theta=\frac{OE}{BE} \\tan\theta=\frac{OE}{\frac{27\sqrt{3}}{2} } \\tan30\times {\frac{27\sqrt{3} }{2} }= OE\\\frac{1}{\sqrt{3} } \times\frac{27\sqrt{3} }{2} =OE\\$

Thus ,apothem OE= 13.5 cm

Now for radius,

We consider ΔOBE

$cos\theta=\frac{base}{hypotenuse} \\cos30= \frac{BE}{OB} \\Cos30 = \frac{\frac{27\sqrt{3} }{2}}{OB} \\OB= \frac{\frac{27\sqrt{3} }{2}}{cos30} \\OB= \frac{\frac{27\sqrt{3} }{2}}{\frac{\sqrt{3} }{2} } \\OB =27 \ cm$

Thus for

Perimeter of equilateral triangle ABC is 81/√3 centimeters,

The radius of equilateral triangle ABC is 27 cm

The apothem of equilateral triangle ABC is 13.5 cm

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