MYP 3 · Maths

INTERPRETING TABLES AND GRAPHS

Line graphs

QUESTION 1 [5 marks] — Criterion A Medium
06121824306am9am12pm3pm6pm9pmTimeTemp (deg C)
The line graph shows the temperature recorded at a weather station throughout one day.06121824306am9am12pm3pm6pm9pmTimeTemp (deg C)
a. State the temperature at 12pm.
[1]
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22°C
b. During which time interval did the temperature rise the fastest?
[2]
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Between 9am and 12pm, the temperature rose from 14°C to 22°C — an increase of 8°C in 3 hours, the steepest rise shown.
c. Find the overall temperature range for the day (highest minus lowest recorded value).
[2]
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Highest: 26°C (3pm). Lowest: 8°C (6am). Range $=26-8=18°C$.
QUESTION 2 [4 marks] — Criterion A Medium
0183654729001020304050Time (min)Height (m)
The line graph shows the height of a hot air balloon over time during a flight.0183654729001020304050Time (min)Height (m)
a. Find the balloon's height at 30 minutes.
[1]
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75 m
b. Describe what happens to the balloon's height between 30 and 50 minutes, and calculate the rate of descent (in m per minute) over this interval.
[3]
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The balloon descends from 75 m to 45 m between minute 30 and minute 50 — a decrease of 30 m over 20 minutes. Rate $=30\div20=1.5$ m per minute.
QUESTION 3 [4 marks] — Criterion B Medium
020406080100012345HourWater Level (cm)
Investigate what a horizontal (flat) section of a line graph represents, using a real scenario.
a. Using the graph (showing water level in a tank being filled), identify the time interval where the graph is flat, and state the water level during that interval.
[2]
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The graph is flat between Hour 1 and Hour 3, with the water level staying at 45 cm.
b. Suggest a real-world explanation for why the water level might stay constant for 2 hours in the middle of a filling process.
[2]
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A likely explanation is that the water supply was paused or turned off during that period (e.g. for a scheduled break, a valve being closed, or a technical issue), before filling resumed afterward.
QUESTION 4 [4 marks] — Criterion C Medium
A classmate says a line graph and a bar graph 'show exactly the same information, just in a different shape', so it doesn't matter which one you use.
a. Explain one key advantage of a LINE graph over a bar graph, specifically related to showing change over a CONTINUOUS variable like time.
[2]
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A line graph directly shows the TREND and rate of change between data points (via the slope of each segment), and can suggest values BETWEEN measured points — a bar graph only shows isolated values at each point, with no visual sense of a continuous trend connecting them.
b. Explain one situation where a BAR graph might actually be more appropriate than a line graph.
[2]
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A bar graph is more appropriate for comparing separate, unrelated CATEGORIES (like sales by different named products, or votes for different candidates) where there's no meaningful 'in-between' value connecting one category to the next — a line connecting them would be misleading.
QUESTION 5 [5 marks] — Criterion D Medium
01836547290Week 1Week 2Week 3Week 4Week 5Week 6WeekWeight (kg)
A person tracking a fitness goal records their weight weekly, shown in the graph.01836547290Week 1Week 2Week 3Week 4Week 5Week 6WeekWeight (kg)
a. Find the total weight lost from Week 1 to Week 6.
[2]
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$$82-65=17 \text{ kg}$$
b. Find the average weight loss per week over the 6 weeks, and use it to predict the weight at Week 8 if the same average rate continues.
[3]
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Average loss per week $=17\div5=3.4$ kg (over 5 intervals from Week 1 to Week 6). Predicted Week 8 weight: $65 - 2\times3.4 = 58.2$ kg.
QUESTION 6 [6 marks] — Criterion A Medium
06121824306am9am12pm3pm6pm9pmTimeTemp (°C)
The line graph shows temperature readings during one day.06121824306am9am12pm3pm6pm9pmTimeTemp (°C)
a. State the temperature at 3pm, and identify the time of the maximum temperature.
[2]
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27°C at 3pm, which is also the maximum.
b. Find the mean temperature across the 6 readings.
[2]
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$$\frac{14+18+23+27+22+16}{6}=\frac{120}{6}=20°C$$
c. Find the RATE of temperature change (°C per hour) between 12pm and 3pm.
[2]
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$$\frac{27-23}{3}\approx1.33°C\text{/hour}$$
QUESTION 7 [3 marks] — Criterion A Medium
01102203304405500246810DaysSubstance (mg)
The line graph shows the mass (mg) of a radioactive substance remaining over time.01102203304405500246810DaysSubstance (mg)
a. Find the mass remaining after 6 days.
[1]
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296 mg.
b. Find the percentage of the ORIGINAL mass (500mg) that remains after 10 days.
[2]
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$$\frac{209}{500}\times100=41.8\%$$
QUESTION 8 [5 marks] — Criterion B Hard
Investigate whether the radioactive decay graph above represents CONSTANT decrease (same amount lost per day) or PROPORTIONAL decrease (same PERCENTAGE lost per day).0110220330440550012345DaysMass (mg)
a. Find the ACTUAL amount lost (in mg) between day 0-1, and between day 1-2. Are these amounts equal?
[2]
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Day 0-1: $500-420=80$mg. Day 1-2: $420-353=67$mg. NOT equal — so the loss is not a constant fixed amount each day.
b. Find the PERCENTAGE lost between day 0-1, and between day 1-2. State what pattern this reveals about how radioactive decay actually works.
[3]
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Day 0-1: $\frac{80}{500}\times100=16\%$. Day 1-2: $\frac{67}{420}\times100\approx16\%$. These percentages ARE approximately equal — revealing that radioactive decay loses a roughly CONSTANT PERCENTAGE of the remaining amount each day (proportional/exponential decay), rather than losing a fixed amount, explaining why the graph curves rather than forming a straight line.
QUESTION 9 [6 marks] — Criterion B Hard
0122436486001234HourDistance (km)
Investigate whether TWO different-looking line graphs (one steep-then-flat, one flat-then-steep) could represent the SAME total change over the SAME time period, just distributed differently.
a. Using the graph shown (steep at first, flattening later), find the TOTAL distance covered over the full 4 hours.
[2]
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52 km total (final value, since start was 0).
b. Now imagine a SECOND journey that instead starts flat and gets steep later, described by values $0,2,4,7,52$ at the same hours ($0,1,2,3,4$). Confirm this journey ALSO covers 52km total, then explain what real-world difference in the JOURNEY (not the total distance) this different shape would represent, compared to the first graph.
[4]
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Second journey final value is also 52km, confirming the same TOTAL distance. However, the shapes represent very different journeys: the FIRST graph (steep-then-flat) suggests fast travel early, slowing down later (e.g. starting energetic, then tiring or hitting traffic) — while the SECOND (flat-then-steep) suggests a slow start followed by a fast finish (e.g. a warm-up period followed by a sprint). Same total distance, but very different speed patterns throughout the journey.
QUESTION 10 [4 marks] — Criterion C Medium
A classmate presents a line graph of monthly sales with NO axis labels or units, saying 'the numbers speak for themselves.'
a. Explain why a graph without axis labels or units fails as effective mathematical communication, even if the shape/trend is visually clear.
[2]
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Without axis labels, a reader has NO way to know what quantity is being measured (sales in dollars? units sold? something else?), what time period each point represents, or what SCALE the numbers are on — a visually clear trend is meaningless without this context, since the same shape could represent wildly different real situations depending on the actual units and values involved.
b. List the minimum THREE pieces of labelling information every properly communicated graph should include.
[2]
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1) A label for the horizontal (x) axis, including units if relevant. 2) A label for the vertical (y) axis, including units. 3) A title or caption stating what the graph represents overall (and ideally the data source/time period).
QUESTION 11 [3 marks] — Criterion C Medium
A student describes a line graph's trend as 'the line goes up a lot', without giving any numbers.
a. Given the graph shows temperature rising from 14°C at 6am to 27°C at 3pm (over 9 hours), rewrite the student's vague description as a precise, quantified statement including the actual rise and the time period.
[3]
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Precise version: 'Temperature rose by $27-14=13°C$ over the 9-hour period from 6am to 3pm, an average increase of approximately $13\div9\approx1.4°C$ per hour.' This version specifies the exact magnitude of change, the time period, and an average rate — far more informative than 'goes up a lot'.
QUESTION 12 [6 marks] — Criterion D Hard
014028042056070002468HoursCharge (mAh)
An electric vehicle's battery charge level is monitored during charging, shown in the graph.014028042056070002468HoursCharge (mAh)
a. Find the AVERAGE charging rate (mAh per hour) over the full 8-hour charge.
[2]
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$$600\div8=75 \text{ mAh/hour}$$
b. The vehicle needs at least 550 mAh to complete a planned trip. Estimate (using the graph's trend) approximately how many hours of charging are needed to reach 550 mAh, and discuss why charging RATE often SLOWS as a battery approaches full capacity in real electric vehicles (a well-known real-world charging characteristic), meaning a simple linear estimate might not be perfectly accurate.
[4]
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Using the roughly linear trend, estimated hours for 550 mAh: $550\div75\approx7.3$ hours. However, real EV batteries typically charge FASTER when nearly empty and SLOWER as they approach full capacity (to protect battery health) — this means a simple linear extrapolation likely UNDERESTIMATES the true time needed near the end of charging, since the last portion of charge often takes disproportionately longer than the earlier, faster-charging portion.
QUESTION 13 [6 marks] — Criterion D Hard
023568JanMarMayJulSepNovMonthUnemployment (%)
An economist tracks a region's unemployment rate over a year.023568JanMarMayJulSepNovMonthUnemployment (%)
a. Find the month with highest unemployment, and the overall change in rate from January to November.
[2]
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Highest: July (7.1%). Change Jan?Nov: $5.0-4.2=0.8$ percentage points increase.
b. A government official claims 'unemployment is under control since it decreased every month from July onward.' Evaluate this claim using the DATA, and discuss what additional information (e.g. data BEYOND November, or the underlying causes of the July peak) would help determine whether this is a genuine sustained improvement or a temporary seasonal fluctuation.
[4]
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The claim is partially supported by the data — the rate DID decrease from July (7.1%) through September (6.3%) to November (5.0%). However, evaluating whether this is 'under control' requires more context: is this a recurring SEASONAL pattern (e.g. summer tourism jobs boosting July unemployment temporarily, then a normal autumn recovery), or a genuine structural improvement? Data from PRIOR years (to check for a repeating seasonal pattern) and data BEYOND November (to see if the improvement continues, plateaus, or reverses) would both be needed to properly assess whether this represents lasting progress.