College

The isosceles triangle has a perimeter of 7.5 m.

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 :

We are given an isosceles triangle with a perimeter of
[tex]$$7.5\text{ m},$$[/tex]
and the shortest side (base) is
[tex]$$y = 2.1\text{ m}.$$[/tex]

In an isosceles triangle, the two equal sides can be labeled as
[tex]$$x.$$[/tex]
Thus, the perimeter is the sum of the two equal sides and the base, which gives the equation
[tex]$$2x + y = 7.5.$$[/tex]

Since we know that
[tex]$$y = 2.1,$$[/tex]
we substitute this value into the equation:

[tex]$$2x + 2.1 = 7.5.$$[/tex]

This is the correct equation to find the value of [tex]$x$[/tex].

Now, to verify the steps, we rearrange the equation to solve for [tex]$x$[/tex]. Subtract 2.1 from both sides:

[tex]$$2x = 7.5 - 2.1.$$[/tex]

Calculating the right side,

[tex]$$7.5 - 2.1 = 5.4,$$[/tex]

so we have

[tex]$$2x = 5.4.$$[/tex]

Dividing both sides by 2 gives

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

Thus, the equation used and the calculations confirm that the equation is

[tex]$$2.1 + 2x = 7.5.$$[/tex]

Therefore, the correct equation is option 4.