In a culture of yeast the active fernment doubles itself in 3 hours. If the quanitity increases at a rate proportional to itself, then in 15 hours, the amount will be. Times original amount.

A sum of money placed at compound interest doubles itself in 3 years. In how many years will it amount to four times itself?

A sum of money placed at compound interest doubles itself in 6 years. In how many years will it amount to 16 times itself?

A sum of money placed at compound interest doubles itself in 4 years. In how many years will it amount to eight times itself ?

A sum of money placed at com pound interest doubles itself in 4 years. In how many years will it amount to four times itself ?

In a certain culture the number of bacteria at any instant increases at a rate proportional to the cube root of the number present at that instant. If the number becomes 8 times in 3 hours, when will the number be 64 times?

A sum of money invested at compound interest doubles itself in 6 years. At the same rate of interest it will amount to eight times of itself in: