Systems of linear equations and inequalities

2000019001

Level: 
B
Four matrices are given: \[\] $\left (\array{ 1& -1& 0\cr 2& 0& 1\cr 1& 1& -1} \right ),$ $\left (\array{ 1& -3& 0\cr 2& -5& 1\cr 1& 0& -1} \right ),$ $\left (\array{ -3& -1& 0\cr -5& 0& 1\cr 0& 1& -1} \right ),$ $\left (\array{ 1& -1& -3\cr 2& 0& -5\cr 1& 1& 0} \right )$ \[\] We want to practice Cramer's rule for solving a system of linear equations. Which of the following systems can be solved using determinants of the four matrices given above?
\[\begin{aligned} x- y = -3 & & \\2x + z = -5 & & \\x + y -z= 0 & & \end{aligned}\]
\[\begin{aligned} x- y-3z = 0 & & \\2x - 5z = 1 & & \\x + y = -1& & \end{aligned}\]
\[\begin{aligned} -3x- y = 0 & & \\-5x + z = 1 & & \\ y -z= -1& & \end{aligned}\]
\[\begin{aligned} x- y = 3 & & \\2x + z = 5 & & \\x + y -z= 0 & & \end{aligned}\]

2000017706

Level: 
C
Which of the systems has its solution graphed on the number line?
\(\begin{aligned} -5x-4 &>11-2x \\ 8-9x &> 2x-69 \end{aligned}\)
\(\begin{aligned} -5x-4 &>11-2x \\ 8-9x& < 2x-69 \end{aligned}\)
\(\begin{aligned} -5x-4 &< 11-2x\\ 8-9x &< 2x-69 \end{aligned}\)
\(\begin{aligned} -5x-4& < 11-2x\\ 8-9x &> 2x-69 \end{aligned}\)

2000017705

Level: 
C
The interval \( \left[ -\frac{12}{11}; \frac6{23}\right)\) is the solution of a system of two linear inequalities with one unknown. Which of the following systems is it?
\(\begin{aligned} \frac{x}3-\frac{x}4 &> 2x-\frac12 \\ 3x+8 &\geq 2-\frac52x \end{aligned}\)
\(\begin{aligned} \frac{x}3-\frac{x}4 &\geq 2x-\frac12\\ 3x+8 &> 2-\frac52x \end{aligned}\)
\(\begin{aligned} \frac{x}3-\frac{x}4& < 2x-\frac12 \\ 3x+8 &\geq 2-\frac52x \end{aligned}\)
\(\begin{aligned} \frac{x}3-\frac{x}4 &> 2x-\frac12 \\ 3x+8 &\leq 2-\frac52x \end{aligned}\)

2000017703

Level: 
C
In the picture, the shaded region corresponds to the set of points that is the solution to one of the given systems of inequalities. Which of the systems is it?
\(\begin{aligned} 3x-4y &>6\\ -1.5x+2y &< 5 \end{aligned}\)
\(\begin{aligned} 3x-4y &< 6\\ -1.5x+2y& < 5 \end{aligned}\)
\(\begin{aligned} 3x-4y &< 6\\ -1.5x+2y &> 5 \end{aligned}\)
\(\begin{aligned} 3x-4y &> 6\\ -1.5x+2y& > 5 \end{aligned}\)

2000017702

Level: 
C
In the picture, the shaded region corresponds to the set of points that is the solution to one of the given systems of inequalities. Which of the systems is it?
\(\begin{aligned} 5x+8y& \leq 27 \\ 9x+2y &< -15 \end{aligned}\)
\(\begin{aligned} 5x+8y &< 27 \\ 9x+2y &\leq -15 \end{aligned}\)
\(\begin{aligned} 5x+8y &\geq 27\\ 9x+2y &> -15 \end{aligned}\)
\(\begin{aligned} 5x+8y &> 27 \\ 9x+2y &\geq -15 \end{aligned}\)

2010011204

Level: 
B
Kamil is able to mow a meadow in \( 12 \) hours. Zdeněk has a better lawn mower and he is able to mow the same meadow in \( 9 \) hours. They have agreed that Kamil starts to mow alone sooner and Zdeněk will join him later so that the total time of mowing is \( 8 \) hours. How long will they mow together?
\( 3 \) hours
\( 5 \) hours
\( 2 \) hours
\( 1 \) hour

2010011203

Level: 
B
The March price of a T-shirt and shorts was \( 900\,\mathrm{CZK} \) together. In April there was on store price adjustment. The price of the shorts decreased by \( 20\% \) and the price of the T-shirt increased by \( 20\% \). So the April price of both together the shorts and the T-shirt was by \( 40\,\mathrm{CZK} \) lower. What was the April price of the T-shirt?
\( 420\,\mathrm{CZK} \)
\( 350\,\mathrm{CZK} \)
\( 440\,\mathrm{CZK} \)
\( 550\,\mathrm{CZK} \)

2010011201

Level: 
C
In the picture, the shaded region corresponds to the set of points that is the solution to one of the given inequalities. Which inequality is it?
\( y \geq -\frac32x+\frac{7}2 \)
\( y \leq -\frac32x+\frac{7}2 \)
\( y > -\frac32x+\frac{7}2 \)
\( y < -\frac32x+\frac{7}2 \)

2010006702

Level: 
B
The augmented matrix of a system of three equations with three unknowns is row equivalent with the following matrix \(A'\). Find the solution of the system. \[ A' = \left(\begin{array}{ccc|c} 2 & 3 & 1 & 7\\ 0 & 3 & 4 & 0\\ 0 & 0 & 5 & 45 \end{array}\right) \]
\([17;-12;9]\)
\([12;10;-9]\)
\([-19;12;9]\)
\([7;0;45]\)