C2 = a2 + b2
29^2 = a^2 + 20^2
841 = a^2 + 400
441 = a^2
a = 21
speed=frequency*wavelength, so frequency=speed/wavelength. frequency=80*0.2
Frequency = 16 Hz
The answer is gases.
hope this help
Answer:
Seven.
Explanation:
A period is a horizontal row of the periodic table. There are seven periods in the periodic table, with each one beginning at the far left. A new period begins when a new principal energy level begins filling with electrons.
