One past or Many?

If 50 minutes ago, it was 45 minutes past four O'clock, how many minutes is it until six O'clock?

How to determine that function is one one or many one

Write one use of wind energy (a) in the past (b) at present.

A transparent sheet of thickness 0.018 mm is pasted on one of the slits of a Youngs slit experiment. If the set - up uses monochromatic light of wavelength 6800 Å , how many fringes will shift due to pasting of the sheet? Take mu sheet = 1.6.

How many electrons are flowing per second past a point in a circuit in which there is a current of 5 amp?