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### Lightning Strikes Again!

 Use more than one branch of mathematics in problem-solving Apply proportional thinking to real-life experiences Choose tools to help in problem-solving

Suggested time allotment

One class period

Student social organization

Students working alone

Assumed background: This task assumes that children have had experience in solving complex problems that are posed in the context of a map. In particular, they should have used rulers to measure distances on a map and dealt with converting from map distances to real distances. The task also assumes some familiarity with the use of a compass to find all points that are a particular distance from a given point.

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OCR for page 115
Measuring Up: Prototypes for Mathematics Assessment Lightning Strikes Again! Use more than one branch of mathematics in problem-solving Apply proportional thinking to real-life experiences Choose tools to help in problem-solving Suggested time allotment One class period Student social organization Students working alone Task Assumed background: This task assumes that children have had experience in solving complex problems that are posed in the context of a map. In particular, they should have used rulers to measure distances on a map and dealt with converting from map distances to real distances. The task also assumes some familiarity with the use of a compass to find all points that are a particular distance from a given point.

OCR for page 115
Measuring Up: Prototypes for Mathematics Assessment Presenting the task: Each child should have access to drawing tools (pencils, a compass, a ruler). Before passing out the student activity materials, the teacher should conduct a short discussion of lightning, focusing especially on the fact that often you see the flash of lightning before you hear the thunder clap. (Children will probably relate their own experiences of seeing a flash before hearing the rumble.) He or she should explain that the two occur simultaneously, but sound travels more slowly than light. Hence, the thunder is heard after the lightning is seen. In fact, the farther away one is from the flash, the greater is the gap between seeing and hearing. The teacher should describe one way to estimate the distance between someone and a lightning flash: Count the number of seconds between the flash and the thunderclap. That number, divided by five, is approximately the number of miles between the person and the lightning. The teacher also can discuss safety-related issues as appropriate. Student assessment activity: The teacher should pass out the student sheets and read the introduction as the class follows along. Discuss questions 1 and 2 as a group to be sure that the students understand the general concepts involved. The students should select tools (ruler, compass, calculator) that are appropriate to the task as they need them. Note: if the student materials are duplicated from this book, the scale may be affected. If necessary, the teacher should redraw the figure ensuring that the distance from point E to point B on the map is 2 inches. The same map can be used without the lightning in questions 5 through 8.

OCR for page 115
Measuring Up: Prototypes for Mathematics Assessment Name _________________________________________ Date ____________ One way to estimate the distance from you to where lightning strikes is to count the number of seconds until you hear the thunder, and then divide by five. The number you get is the approximate distance in miles. People are standing at the four points A, B, C and D. They saw lightning strike at point E. Because sound travels more slowly than light, they did not hear the thunder right away. Who heard the thunder first? ___ Why? Who heard it last? ___ Why?

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Measuring Up: Prototypes for Mathematics Assessment One of the people heard it after 12 seconds. Who was it? _________ Explain your answer. After how many seconds did the person at B hear the thunder? _____ Show how you know. Now suppose lightning strikes again at a different place. The person at A and the person at C both hear the thunder after the same amount of time. Show on the map below where the lightning might have struck. In question 5, are there other places where the lightning could have struck? _________ If so, show as many of those places as you can.

OCR for page 115
Measuring Up: Prototypes for Mathematics Assessment Lightning struck again! The person at point A heard the thunder 5 seconds after she saw the lightning. Show as many points as you can where the lightning could have struck. The person at point C heard the thunder from that same lightning bolt 15 seconds after the lightning struck. Show where the lightning could have struck.

OCR for page 115