Log Questions

[asian_91]

Hey, can someone help me out here with  a few of my log questions?

A population of bacteria is observed to double in number each minute. If a single bacteria is placed into a test tube, after how many minutes will the test tube contain at least 600 such bacteria?

Formula db= 20 log S-26 approximately describes the relationship between pressure of a sound in micropascals and its reading on decibel scale (db). If a bird sings and produces a sound pressure of 400 uPa and a "Jumbo Jet" produces a reading of 100Pa, use the formula to convert these to their corresponding decibel values.

A=Ae^-kt

After how many years would 10 grams of radium decay so that only 8 grams remain? ( Its half life is 1590 years)

Solve: log 5/36 - log 5/9 = -log 4

Thankx

[Mao]

1.

2. plug the numbers into the formula,

3. , find k, then find