A student investigated the effect of different concentrations of a plant hormone, gibberellin, on the germination rate of barley seeds.
The concentrations of gibberellin used in six petri dishes were:
Dish 1 is a control containing no gibberellin. Why did the student include Dish 1 in the investigation?
Calculate how many times more concentrated the gibberellin is in Dish 6 than in Dish 2. Show your working.