AMOUNT OF BACTERIA PRESENT
Time Amount
1:00 P.M. 8.0 grams
4:00 P.M. x grams
7:00 P.M. 12.4 grams
Data for a certain biology experiment are given in the table above. If the amount of bacteria present increased by the same fraction during each of the two 3-hour periods shown, how many grams of bacteria were present at 4:00 P.M.? Select the correct option:
A) 12.0	B) 12.1	C) 12.2	D) 10.0	E) 10.4

Rationale: the question says that bacteria increased by same fraction , not by same amount in 2 intervals of 3 hours . let x represent the amount of bacteria present at 4 : 00 pm . since the fractional increase must remain constant from 1 to 4 pm as it is from 4 pm to 7 pm : fractional increase from 1 pm to 4 pm = x / 8.0 fractional increase from 4 pm to 7 pm = 12.4 / x x \ 8 = 12.4 \ x x ^ 2 = 12.4 * 8 x = 10 answer : d
Answer: D