High School

The isosceles triangle has a perimeter of 7.5 m.

The sides are: [tex]\( x \)[/tex], [tex]\( y \)[/tex], [tex]\( x \)[/tex]

Which equation can be used to find the value of [tex]\( x \)[/tex] if the shortest side, [tex]\( y \)[/tex], measures 2.1 m?

A. [tex]\( 2x - 2.1 = 7.5 \)[/tex]

B. [tex]\( 4.2 + y = 7.5 \)[/tex]

C. [tex]\( y - 4.2 = 7.5 \)[/tex]

D. [tex]\( 2.1 + 2x = 7.5 \)[/tex]

Answer :

To find the correct equation that matches the given conditions for the isosceles triangle, we need to understand the information provided:

1. The perimeter of the isosceles triangle is 7.5 meters.
2. The triangle has two equal sides labeled as [tex]\( x \)[/tex] and the shortest side labeled as [tex]\( y \)[/tex].
3. The shortest side [tex]\( y \)[/tex] measures 2.1 meters.

The formula for the perimeter of a triangle is:
[tex]\[ \text{Perimeter} = x + x + y = 2x + y \][/tex]

Given that the perimeter is 7.5 meters, we can substitute the known value of [tex]\( y \)[/tex] into this equation. Let's rewrite the equation:

[tex]\[ 2x + y = 7.5 \][/tex]

Now, substitute [tex]\( y = 2.1 \)[/tex] into the equation:

[tex]\[ 2x + 2.1 = 7.5 \][/tex]

To solve for [tex]\( x \)[/tex], we simply rearrange the equation:

1. Subtract 2.1 from both sides to isolate the terms with [tex]\( x \)[/tex]:

[tex]\[ 2x = 7.5 - 2.1 \][/tex]

2. Simplify the right side:

[tex]\[ 2x = 5.4 \][/tex]

3. Divide both sides by 2 to solve for [tex]\( x \)[/tex]:

[tex]\[ x = \frac{5.4}{2} \][/tex]
[tex]\[ x = 2.7 \][/tex]

So, the correct equation that can be used to find the value of [tex]\( x \)[/tex] is:

[tex]\[ 2.1 + 2x = 7.5 \][/tex]

Therefore, the correct choice from the given options is:

- [tex]\( 2.1 + 2x = 7.5 \)[/tex]

This equation properly represents the relationship and checks out with the given information.