bacteria

[dikku07]

AMOUNT OF BACTERIA PRESENT

Time Amount

1:00 P.M. 10.0 grams

4:00 P.M. x grams

7:00 P.M. 14.4 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.?


A. 12.0

B. 12.1

C. 12.2

D. 12.3

E. 12.4


my answer isn't matching OA and I really don't get the explanation of OA. OA will come later

[sreak1089]

Is it C (12.2)?

[ssmiles08]

let f be the fraction increased during each of the 3 hour period.

10*f = x

x*f = 14.4 or f = 14.4/x

we want to find x.

10*(14.4/x) = x

144/x = x

x^2 = 144

x = +12 or -12. (-12 is invalid b/c there can not be negative grams)

x = 12 grams. IMO A.

[mp2437]

Agree with ssmiles08. "A" should be right answer.

[dikku07]

OA is A

I just tried 10+2.2=12.2
12.2+2.2=14.4

but i'm still wondering since increasing it by fraction 2.2, it matches the increase. but say, if the rate is 2 than how come it will be 12+2 will lead to 14.4 (if formula is not used)