Concept 2 of 7
Line Graphs: Track Change Over Time
Today's big idea
Line graph: dots connected by lines show a trend over time.
Going up = increasing. Going down = decreasing. Flat = no change.
How it works
👀 What's going on?
A plant on your windowsill grows a little every week. Write the heights in a list and you see numbers. Plot them and join the dots, and you see the growing.
💡 Here's the trick
Look at the graph above. Time runs along the bottom and the measured amount runs up the side. A rising line means the value went up between those two times, and a flat line means no change.
🪄 How to do it
- 1.Find your time on the graph above and go straight up.
- 2.Stop at the line, then read across to the value.
- 3.Subtract two values to find a rise or a fall.
✍️ Try it
A line graph of a baby's mass shows 5 kg in May, 7 kg in June, 7 kg in July, 8 kg in August. How much mass was gained from May to August? Then: which month pair shows no change?
From May to August the mass went 5 kg up to 8 kg, a gain of 3 kg. The line is flat from June to July, since both months read 7 kg.
⚠️ Watch out
You might be thinking a steep line always means a big number. It means a big change. A line can climb steeply from 2 to 6 while another sits flat at 90.
🌟 Why this matters
Doctors plot your height and mass year by year, and a weather app draws the day's temperature the same way. One look shows whether things are climbing, falling or holding steady.
Exam tip: When a question asks for the greatest change, work out every step, not just the two ends.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“Daily sales over 5 days: 20, 25, 18, 30, 22. What was the PEAK?”
- 1
List the data points
20, 25, 18, 30, 22. 📈
- 2
Scan for the highest
30 is bigger than every other.
- 3
Identify the day if needed
Day 4 (= Thursday in the source).
- 4
Answer ✓
Peak = 30.
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
A line graph shows change over time. The higher the point, the bigger the value.
Daily Temperature (°C)
STEP 1 OF 3
Tap the PEAK — the highest point on the line.
Quick check
✅ VERIFICATION
A line graph shows a shop's sales: Mon ₹300, Tue ₹450, Wed ₹400, Thu ₹500. Between which two days did sales FALL?
⚡ Finish the activity above first to answer.
Keep going!
Up next: Pie Charts
Full circle = 360° = 100% = the total.