The size of a bacteria is 1 µ. Find the number of bacteria in 1m length.

The distance of the nearest star, Proxima Centauri, from the Earth is 4.0 x 10¹³ km. Express it in light year.

It takes time 8 min for light to reach from the sun to the earth surface. If speed of light is taken to be 3 x 10⁸ms^-1, find the distance from the sun to the earth in km.