# Radius of a sector of a circle?

What is the radius of a sector of a circle with a central angle of measure 90° and whose area is 4π cm2?

1) 8cm

2) 4cm

3) 12cm

4) 3/4 cm

What is the radius of a sector of a circle with a central angle of measure 45° and whose area is 9/8πcm^2

1) 8cm

2) 4/3cm

3) 9/4cm

4) 3cm

Relevance
• 8 years ago

1:

area of a sector=90/360xπ(r^2)

4π=0.25π(r^2)

cut out π

4/0.25=r^2

taking square root on both sides:

r=4

2:

area of a sector=90/360xπ(r^2)

9/8πcm^2=45/360π(r^2)

following the same procedure as done above