Answer: Katherine Johnson's knowledge of (mathematics) was instrumental in the return of the Apollo astronauts from the Moon to Earth.
Sound waves are not able to travel in a vacuum, sound requires a medium such as air or a solid for example. Satellites are indeed in space, but radio waves are not sound waves they are a form of light. Light can travel in a vacuum so the messages that satellites beam back to Earth are light waves not sound waves, that is why it is possible.
The answer is mass. I have to comment more than 20 characters.
Answer:
20 Ω
Explanation:
Voltage, current, and resistance are related by Ohm's law:
V = IR
40 V = (4 A) R
R = 10 Ω
The total resistance of the circuit is 10 Ω.
Resistors in parallel have a total resistance of:
1/R = 1/R₁ + 1/R₂
1 / (10 Ω) = 1 / (20 Ω) + 1/R₂
R₂ = 20 Ω