Grade 8 Algebra: Comparing Functions

Name: ______________________Date: ____________Score: ____ / 8

Level 3

Real-life comparisons

1. ${x}$ = hours, ${y}$ = miles. Which car is faster:
$\begin{array}{ll} \textbf{A:} & y = 55x \\[14pt] \textbf{B:} & \begin{array}{c|ccc} x & 1 & 2 & 3 \\ \hline y & 60 & 120 & 180 \end{array} \end{array}$
2. ${x}$ = months, ${y}$ = total cost in dollars. Which gym has the lower joining fee:
$\begin{array}{ll} \textbf{A:} & y = 30x + 50 \\[14pt] \textbf{B:} & \begin{array}{c|ccc} x & 1 & 2 & 3 \\ \hline y & 65 & 100 & 135 \end{array} \end{array}$
3. ${x}$ = months, ${y}$ = total cost in dollars. Which gym costs less per month:
$\begin{array}{ll} \textbf{A:} & y = 30x + 50 \\[14pt] \textbf{B:} & \begin{array}{c|ccc} x & 1 & 2 & 3 \\ \hline y & 65 & 100 & 135 \end{array} \end{array}$
4. ${x}$ = weeks, ${y}$ = dollars saved. Who saves more each week:
$\begin{array}{ll} \textbf{A:} & y = 15x + 20 \\[14pt] \textbf{B:} & \begin{array}{c|ccc} x & 0 & 2 & 4 \\ \hline y & 40 & 64 & 88 \end{array} \end{array}$
5. ${x}$ = minutes, ${y}$ = liters left. Which tank drains faster:
$\begin{array}{ll} \textbf{A:} & y = -4x + 100 \\[14pt] \textbf{B:} & \begin{array}{c|ccc} x & 0 & 5 & 10 \\ \hline y & 80 & 55 & 30 \end{array} \end{array}$
6. ${x}$ = minutes, ${y}$ = liters left. Which tank starts with more water:
$\begin{array}{ll} \textbf{A:} & y = -4x + 100 \\[14pt] \textbf{B:} & \begin{array}{c|ccc} x & 0 & 5 & 10 \\ \hline y & 80 & 55 & 30 \end{array} \end{array}$
7. ${x}$ = weeks, ${y}$ = height in cm. Which plant grows faster:
$\begin{array}{ll} \textbf{A:} & y = 0.5x + 12 \\[14pt] \textbf{B:} & (2, 10),\ (6, 13) \end{array}$
8. ${x}$ = texts, ${y}$ = cost in dollars. When do the plans cost the same:
$\begin{array}{ll} \textbf{A:} & y = 0.1x + 20 \\[14pt] \textbf{B:} & \begin{array}{c|ccc} x & 0 & 100 & 200 \\ \hline y & 10 & 40 & 70 \end{array} \end{array}$