arithmetic sequence

Mar 2019
TTF area
Question (given): A pharmacy sees that its sales of cold medications increase steadily from the beginning of May. Their sales record shows that last year they sold 26 packets of cold tablets in the first week in May. The sale of cold tablets increased by seven packets each week.

1. on the figures find the total number of packets sold over the 16 weeks of winter.

I found them to = a=26 d=7 n=16

using Sn= n/2[2a+(n-1)d] it equals Sn=16/2[2x26+(16-1)7)] S16=1256?

so 1256 packets were sold over 16 weeks?

2. The drug phenylephrine

One tablet of cold medication contains 5.0 milligrams (mg) of phenylephrine.

This table shows the decay of this drug in the blood over a period of 4 hours after it is taken.

Find an equation which models the decay of the drug phenylephrine, and use the equation to find the level of the drug in the blood 6 hours after it is taken.

T2/T1 4/5=0.8, 3.2/4=0.8 r=0.

Tn = 5 x 0.8^(n-1) T75x0.8^6 = 1.31072 or 1.3 after 6 hours there is 1.3mg of drug in the blood?


Dec 2019
Problem #1 is correct. As regards the second problem, I cannot understand what model of fit you used. The concentration of drug in blood generally follows an exponential model.