33
Graphs
Textbook: Part 1, lesson 33, pp. 102–104
GoalRead a graph that shows how a quantity changes over time.
New words
graph · grafikchange · o‘zgarishbroken line · siniq chiziqtemperature · harorat
Explanation
A graph shows data as a straight, broken or curved line. It shows how a quantity changes over equal time intervals. In a distance–time graph a straight line from the origin means travelling at a constant speed and a horizontal segment means a stop. From the points of a graph we read the greatest and least value, the change and the mean.
Worked examples
Midday temperatures over five days: 12°, 15°, 14°, 18°, 16°. The highest is 18° and the mean is (12 + 15 + 14 + 18 + 16) : 5 = 15°.
A car: 80 km after 2 hours, still at 80 km after 3 hours (a stop), 160 km after 5 hours. The stop lasted 1 hour; then 80 km in 2 hours – 40 km/h.
Class activity
“Bring the graph to life”: children act out a distance–time graph (fast walking, slow walking, stopping) while classmates draw the graph.
Practice
1
A graph shows midday temperatures of 12°, 15°, 14°, 18°, 16° over five days. What is the highest temperature in degrees?
18
2
What is the mean temperature over those five days, in degrees?
15
3
A cyclist's graph is a straight line: 60 km in 4 hours. What is the speed in km/h?
15
4
A car's graph has a horizontal segment from hour 2 to hour 3. For how many hours did it stand still?
1