Algebra Two- Senior

Question

mass of 380 grams decays by 16.5% per minute. To the nearest minute, how long will it be until there are 70 grams of the element remaining?

Answer 1

380-16.5%=380-62.7=317.3 9.5 minutes

317.3 =317.3-52.35=264.95

264.95 = 264.95-43.72=221.23

221.23 =221.23-36.5=184.73

184.72 =184.73-30.48=154.25

154.25 =154.25-25.45=128.79

128.79 =128.79-21.25107.54

107.54 =107.54-17.74=89.79

89.79 =89.79-14.82=74.98

74.98 =74.98-12.37=62.61

Answer 2

Decay is just like depreciation when thinking about money!

So, the formula at hand is 70 = 380(1-.165)^t

Solving for t we find that t = 9.38 minutes to get to 70 grams from 380 grams