As a spacecraft passes directly over Cape Canaveral, radar pulses are transmitter toward the craft and are then reflected back toward the ground. If that total time interval was 3.00x10^-3 s, how far above the ground was the spacecraft when it passed over Cape Canaveral?

I know v=d/t and d=v/t. Using my calculator, I've punched in different numbers and continuously end up with an incorrect answer. This is what I've done:

d=343/.003.

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Q2:

Find the illumination 8.0m below a 405lm lamp. The answer I received was: .504lx. Is this answer correct?

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Q3:

Two lamps illuminate a screen equally. The first lamp has an intensity of 12.5cd and is 3.0m from the screen. The second lamp is 9.0m from the screen. What is its intensity?

I know I need to use P=4*pi*(I), but there is no variable included for distance (d). Another formula given is: Eill=P/(4*pi*d^2). How should I go about solving this problem now? Lastly, I am cognizant that 1lm=1cd.

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Q4: A 15cd point source lamp provide equal illuminations on a wall. if the 45cd lamp is 12m away from the wall, how far from the wall is the 15cd lamp.

Again, there is no variable for distance in the equation: P=4*pi*I.