9.2 Small Group · Group 2
Second Challenge Form · Non-Routine Extension · Same Standard, New Problems
graph · table of values · Procedural Fluency · Real-World Applications
- You already can do this. So we go up a level, not up a number: find what is always true, show it a second way, and be ready to defend it with a reason instead of an answer.
- Each ticket costs $45, so the total cost is 45 times the number of tickets: 1 ticket is $45, 2 tickets are $90, 3 tickets are $135.
- The number of tickets is the independent variable, so it goes first in each ordered pair: (1, 45), (2, 90), (3, 135).
- I label one axis 'Number of tickets' and the other 'Total cost ($)', then plot each pair as a point.
- The points rise to the right: as the number of tickets increases, the total cost increases.
- The tram travels 1,200 feet every minute. Which quantity is independent — time or distance?
- Time is independent, so our pairs look like (minutes, feet): (1, 1200), (2, 2400), (5, 6000).
- The ascent takes 15 minutes, so the last point is (15, 18000) — because 15 times 1,200 is 18,000 feet.
- Each point means: after THIS many minutes, the tram has traveled THIS many feet.
- Now prove it: say why that move had to work at all — not just that it did.
- Sentence frame — convince a skeptic: "My method works because ___ . It would stop working if ___ ."
- graph (gráfica) — A picture on a coordinate plane that shows how two quantities are related.
- table of values (tabla de valores) — A list of matched pairs of values that shows a relationship using numbers.
- ordered pair (par ordenado) — Two numbers written as (x, y) that name one point on a graph. The independent variable comes first.
- axis (eje) — One of the two number lines that frame a graph. Each axis is labeled with a quantity from the problem.
- coordinates (coordenadas) — The numbers in an ordered pair that tell how far to move along each axis to reach a point.
- Reversing the coordinates of a point — writing (cost, tickets) instead of (tickets, cost). The independent variable always comes first in the ordered pair.
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1 MULTIPLE CHOICE
A different event's ticket graph passes through the point (4, 100). What does one ticket cost, and where would the point for 7 tickets sit?
- A$25 each, and the point would be (7, 175)
- B$25 each, and the point would be (175, 7)
- C$400 each, and the point would be (7, 2800)
- DThere is not enough information to find the cost of one ticket
✏️ Workspace & Solution Steps
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2 MULTIPLE CHOICE
Two trams both start at the bottom at 0 minutes. One climbs 1,200 feet each minute, the other 900. Both are graphed on the same axes with minutes across. Without working out a single point, how can you tell which line belongs to the faster tram?
- AIts line rises more steeply — it gains more feet in the same minute
- BIts line starts higher up the vertical axis
- CIts line is longer than the other one
- DYou cannot tell without plotting points for both
✏️ Workspace & Solution Steps -
3 MULTIPLE CHOICE
Claim: “If two quantities grow together, the points on their graph always lie on a straight line.” Always, sometimes, or never true?
- ASometimes — only when the quantity grows by the same amount each step
- BAlways — growing together is what makes a line
- CNever — real data never lines up
- DSometimes — only when both quantities are measured in the same unit
✏️ Workspace & Solution Steps
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4 OPEN RESPONSE
Every graph in this lesson rises to the right. Invent a situation where the dependent quantity goes DOWN as the independent quantity goes up. Give three ordered pairs, say what each quantity is, and describe what your graph looks like.
✏️ Mathematical Justification & Response -
5 OPEN RESPONSE
On the tram graph — minutes across, feet climbed up the side — a classmate marks the point (0, 0) and says it is meaningless. Do you agree? Say what (0, 0) claims about the tram, and why the line passes through it.
✏️ Mathematical Justification & Response -
6 ERROR ANALYSIS
Fix our table's thinking
- 1The problem:Why is the line on the football ticket graph dashed instead of solid?
- 2A classmate at our table answered:The graph is unfinished
Which step contains the error? Explain the mathematical misconception and write the correct calculation below.
✏️ Corrected Mathematical Work & Explanation
Writing Task: Justify why your mathematical solution is accurate and complete.