hey, guys, I have a big test today and I did not study for it at all, any help would be much appreciated

In the rectangle below ac=30 units what is de

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)

10% of 1,900,000. show me how you got the answer