I have went through electrical engineer schooling, and one of thing any person needs to remember is the Ohms law. So how current, voltage, resistance and power work and effect each other. This is how I remember it.
PUIMURI = this means harvester in Finish, IT’s the only thing you have to remember. Now when you need to use it, draw it like this. If you want to use V and Not U. It’s PVI M VRI. But that is much harder to remember at least to Finns.
Draw it at the top of your exam. Notice that the M forms these triangles. From this you can easily read fast, that I = P/U, U=P/I, P = I x U . I = U/R, R = U/I, U = R x I .
So it someone askes, how much currect will be drawn if Appliance has 2200Watts. You know the Power=P, You know the mains voltage, 220Volts= U. Now just remember the PUIMURI, and This triangle and you know that the I = P/U. 2200W/220V = 10 Amps.
And ones you use this triangle for some time, at least I can remember it and draw it inside my head and solve any outcome out of it. And calculate these quite fast in mind.
It’s also possible to combine these two, so if you don’t know the voltage. You can solve the other side first that U must be I x R. Then Add this to the U at PUI triangle. So you get P = I x I x R = -> P = I^2 x R