Abacterial culture is known to grow at a rate proportional to the amount present after 1 hour, 1000 strands of the bacteria are observed in the culture, and after 4 hours, 3000 strands. find the number of strands of bacteria originally in the culture.

This type of situation applies first order type of equation.  In this case, the equation is ln( A0/A1) = kt when A1 is 1000, t is 1 hour. that is ln (A0/1000) = k the other condition is represented by ln (A0/3000) = 4k The two equations tell that Ao is equal to 694 strands.

Sis less than or equal to 75 (bottom left)