When examining the soil of the potato field the quantity of rain worms was calculated on test plots ...: ответ на тест 1054922 - Экология

When examining the soil of the potato field the quantity of rain worms was calculated on test plots 100*100 centimeters in size. In 10 test plots there were found 120  rain worms. To combat potato beetle the field was pesticide-laden and then the rain-worm were recalculated in the same test plots. There were only 30 rain worms found. Calculate the population density of rain worms per  square meter before and after pesticide-laden; calculate by how many times the population density has become lower under the impact of pesticide. (Give your answers in the answer fields as whole numbers separated by a comma without any spaces.)