At 1:00 pm, there were 10.0 grams of bacteria. The bacteria increased to x grams at 4:00 pm, and 25.6 grams at 7:00 pm. If the amount of bacteria present increased by the same fraction during each of the 3-hour periods, how many grams of bacteria were present at 4:00 pm?  Choose the most appropriate option
A) 15.1 B) 15.4 C) 15.7 D) 16.0 E) 16.3
Let x be the factor by which the bacteria increases every three hours.   At 4:00 pm, the amount of bacteria was 10x and at 7:00 pm it was 10x^2.   10x^2 = 25.6   x^2=2.56   x=1.6   At 4:00 pm, the amount of bacteria was 10(1.6)=16 grams.   The answer is 16.0.
<result>D</result>
At 1:00 pm, there were 10.0 grams of bacteria. The bacteria increased to x grams at 4:00 pm, and 25.6 grams at 7:00 pm. If the amount of bacteria present increased by the same fraction during each of the 3-hour periods, how many grams of bacteria were present at 4:00 pm?