TASK CARD: Changing Dimensions
TEKS 8.10a Describe the resulting effects on perimeter and area when the dimensions of a shape are changed proportionally.
Materials Needed: 6 sheets of card stock with cm grid copied onto it, formula chart, scissors, marker, changing dimensions record sheet.
Complete each task stated with a partner one at a time and record the information on the Changing Dimensions recording sheet as you go.
NOTE* conserve space on your cm grid as you proceed through each task.
• On the cm grid paper, sketch a right triangle with a base of 3 cm and a height of 4 cm. Record the dimensions, the perimeter, and area for this triangle on your recording sheet. (HINT: you will need to use the Pythagorean Theorem to help you find the perimeter of this triangle.)
• Cut out the triangle and set aside. Label this triangle with an “O” to represent the original triangle.
• Apply the scale factors listed on your record sheet to the original triangle. Draw these enlarged or reduced figures one at a time on the remaining cm grid paper. Record their dimensions on the recording sheet.
• Using the original cut out triangle, stamp and trace it with a marker onto the enlarged triangles as many times as it will fit. (NOTE* you may have to rearrange area to use all space inside the enlarged figure.)
• Use the stamped images to help you to find the new perimeter and new area of the enlarged right triangles. Record the new area and perimeter on your recording sheet.
• Repeat the above process with each shape listed on your recording sheet.
• Lastly, answer the questions on the Changing Dimensions Final Reflections sheet. Turn in your recording sheet and your final reflections sheet to your teacher.