Jose is two years older than half his sister's age. Jose is 12 years old. Which equation can be used to find the age of Jose's sister. A. 2a+2=12

B. a-2=1/5(12)

C. 1/2 (2a-2)=12

D. 1/2a+2=12

The answer is either a or c

Given:
population: 2,100 bacteria
petri dish radius : 40 millimeters

Area of a circle = π r²
A = 3.14 * (40mm)²
A = 3.14 * 1,600 mm²
A = 5,024 mm²

Population density is the measurement of the population per unit area or unit volume:

population / area  = 2,100 / 5,024mm² = 0.41799
 
The approximate population density is 0.42 bacteria per square millimeter