Ex) Point A Ex) line segments BA, Ac, & AD Ex) line segment BC Ex) line segment BC & EF The diameter is a type of chord Think perimeter – circumference is about 3 times the diameter R = radius & D = Diameter Formulas: R = D ÷ 2 D = R • 2 Exploring Circles Activity 1 Modified from the Virginia Department of Education Refer to the notes page provided for vocabulary. Directions: 1. Cut out the circle provided 2. Fold the circle in half and then unfold it. Use a colored pencil and a straight edge (i.e. ruler) to trace the line segement formed by the crease you just made, and label this line “diameter” 3. Fold the circle in half again, but not along the same fold as before. Unfold it and label the point where the two creases intersect (cross) “center”. 4. Use a different colored pencil and trace this new crease going from the “center” to one “edge”. You will only trace half of this crease! The line you just drew is called the “radius”. 5. Make one more crease, but this time make it where it does NOT go through the center. Open and trace this new line with a different color. This line is called the “chord”. 6. Flip your circle over and trace along the outside edge of the circle with another different color. The perimeter of a circle is called the “circumference”. Exploring Circles Activity 2 Exploring Circles Activity 3 Math 5 Common Assessments (Revised 2016 SOLs) SOL 5.10 Diameter, radius, chord, circumference SOL 5.10 1. Circle a box to choose each answer you want to select. You must select three correct answers. Identify each line segment that is a radius of the circle. ���� ���� ���� ���� ���� SOL 5.10 2. Look at the circle. Point M is the center of the circle shown. N M Which line segment is a radius of the circle? L A MN B �LO���� C ON���� O ���� D LN SOL��� �5.10 3. The diameter of the circle is – N A MN M B LN���� � C �NO��� D �LM���� L ����� O SOL 5.10 4. Line segment is a – N A diameter ���� B circumference M C radius D chord L O SOL 5.10 5. Which statement accurately describes the relationship between and ? Y �A��� IY is �½�� the length of IH H B IH� is two times the size�� �of IY C IY��� is two times the size of IH� IY IH D � is equal to ��� I � ��� SOL 5.10 6. Juan and Erica both drew congruent circles and marked the center points as R. They each drew a line segment inside their circle as shown. Juan’s Circle Erica’s Circle R R Which statement best describes the line segments in Juan’s and Erica’s circles? A Juan’s line segment shows a diameter, and Erica’s line segment shows a radius. B Juan’s line segment shows a diameter, and Erica’s line segment shows a chord. C Juan’s line segment shows a radius, and Erica’s line segment shows a diameter. D Juan’s line segment shows a chord, and Erica’s line segment shows a diameter. SOL 5.10 7. What statement best describes the relationship between the circumference of circle B and ? A The circumference of circle B is about half of �CA��� A B CA is about half of the circumference of circle B ���� C B C The circumference of circle B is a little more than ���� three times CA D CA is twice the circumference of circle B ���� ���� SOL 5.10 8. Which statement is true? A Chords are always diameters. B Radii are equal to diameters. C Diameters are about half of radii. D Diameters are always chords. SOL 5.10 9. Which statement is true? A A diameter can go around the outer edge of a circle a little bit more than three times. B A radius is two times the circumference. C A diameter is three times a radius. D A radius can go around the outer edge of a circle a little bit more than three times. SOL 5.10 10. Another name for a diameter is a _____________________. A Circumference B Length C Radius D Chord Answer Keys Activity 1 Activity 2 Activity 3 Common Assessment 1. QR, OQ, OP, 7. C 2. A 8. D 3. B 9. A 4. D 10. D 5. C 6. C .