When dividing fractions, why do we invert (find the reciprocal) and multiply?

If the speed of an electromagnetic wave is 100,000 cm/s and its wavelength is 100 cm, what is its frequency? a) 100,000 cycles per second (hz) b) 1 × 10-3 cycles per second (hz) c) 10,000,000 cycles per second (hz) d) 1,000 cycles per second (hz)

Which ordered pair identifies a point in quadrant iv? a) (2, 5) b) (0, 1) c) (-1, -1) d) (12, -5) which quadrant is (-4,-6) in? a) i. b) ii. c) iii. d) iv.

Sara goes on a slingshot ride in an amusement park. she is strapped into a spherical ball that has a radius 3*10^2 of centimeters. what is the volume of air in the spherical ball? use this formula: volume of a sphere=4/3pi,r^3 , where r is the sphere’s radius.