4/26 HG Live Review (10-1)

Circles!

Area & Circumference

Multiple Choice

Q1: A circular pie has an area of 706.5 cm². What is the radius of the pie?

• 225 cm

• 30 cm

• 15 cm

• 112.5 cm

Q1: A circular pie has an area of 706.5 cm². What is the radius of the pie?

•  $706.5=\pi r^2$  

• Divide by pi:      $r^2=224.8859...$  

•  $r^2=225$  

•  $r=15$  

Multiple Choice

Q2: I wrapped a tape measure around the trunk of the tree and it was 10 feet. What is the diameter of the tree?

• 1.59 ft

• 31.4 ft

• 3.18 ft

• 10.11 ft

Q2:  Circumference = 10 feet

•  $C=d\pi$  

•  $10=d\pi$  

• Divide by pi:  

•  $d=3.18\ feet$  

Multiple Choice

Q3: Alex has trained his puppy, Popper, to jump through a ring. According to Alex's calculations, the ring has an area of 50.265 square feet. What is the approximation of the ring's circumference ?

• 50 ft

• 8 ft

• 25 ft

• 35 ft

Q3:   $50.265=\pi r^2$  

•  $r^2=15.99...$  

•  $r^2=16$  

•  $r=4$  

•  $C=8\pi$  

•  $C=25.13\ feet$  

Multiple Choice

Q4: Sally tried to solve for the area of circle. Her work is shown. What mistake did Sally make.

• Sally squared π incorrectly.

• Sally multiplied the π and radius incorrectly.

• Sally used diameter instead of the radius.

• No mistake. Sally solved the problem correctly.

Q4:  Sally's Mistake:

• She used the diameter instead of the radius

•  $A=\pi\cdot6^2$  

•  $A=36\pi$  

•  $A=113\ square\ feet$  

Today:

Angles & Arcs