Given that 500 colonies were observed on ampicillin plate after transformation. 1 colony represents 1 transformed bacteria because each colony is assumed to have grown from one single bacteria. Hence, 500 bacteria had transformed from 5*10^6 bacteria.
Fraction of cells that got transformed = (Number of cells that were transformed/ Number of total cells)
= 500/(5*10^6)
= 1/10^4
Hence, 1/10^4 cells were transformed in experiment.
