Are two circles concentric if they share the same radius?

The radius of the circle is 4 cm and the measure of the central angle is 90° the area of the sector with a central angle measuring 90° and radius of length 4 cm is vt cm the triangle in the sector is 4 cm the area of the triangle is v/cm² the area of the segment of the circle is (471 - ) cm?

One line passes through (-7,-4) and (5,4) . another line passes through the point (-4,6) and (6,-9)

Benjamin is making bow ties. how many 1/2yards lomg bow ties can he make if he has 18 feet of fabric?