The three scales shown below are balanced. The mass of $\boldsymbol{\lambda}$ is $1 \mathrm{~kg}$. Which of the other objects, (circle, square and triangle), has a mass of $1 \mathrm{~kg}$ ?

![](https://cdn.mathpix.com/cropped/2024_04_17_d0cbae19e125c7a52478g-1.jpg?height=282&width=1659&top_left_y=2057&top_left_x=295)
Suppose the mass of $\boldsymbol{\Delta}$ is $x \mathrm{~kg}$, the mass of $\square$ is $y \mathrm{~kg}$, and the mass of $\square$ is $z \mathrm{~kg}$.

From the first scale, we have that $3 y=2 x$ or $y=\frac{2}{3} x$.

From the third scale, we have that $2 y=x+1$, so we can substitute $y=\frac{2}{3} x$ into this equation

to get $\frac{4}{3} x=x+1$. This can be solved for $x$ to get $x=3$.

Substituting $x=3$ into $3 y=2 x$ gives $3 y=6$ so $y=2$.

From the third scale, we have that $5 z=x+y=5$, and substituting $x=3$ and $y=2$ gives $5 z=5$ or $z=1$.

ANSWER: