Question

Please let me know if I answered correctly, if not please explain the problem.

4. The retention by students of material learned earlier is given by R(t) = 82 – 15 In (10+4 + 1), where t is time in weeks since the material was taught and R is the percent of materia retained. Find the RATE of retention after 5 weeks. (Hint: Rate of retention is the derivative.) Use good calculus notation and answer with a sentence. I R(t) = 82 - 151n (104 + 1) 15 R'(t) = 0 - 10+*+1 ( 40t3 + 0) -60(125) R'(5) = 1+6250 R'(5) = - 1.200 6251 -7500

Answer 1

No your ariswer is not correct. These is slight mistake, Here Retension by Student of material learned earlicer is given by, RCU) = 82-15 en Clot"+1) so, r'ct) (82-15 ln cloth +1) dt d (idere =0 cend d In (f(t)) ct J d fet) fcc) dt 's (10€+ is) dclot'+03 (+)) Tott, (40++0) ") =) Rict) akt dt kdth=kntno dt 3 =) pict 600 t 10+4 + 1 of retension after t weeks is So, rate given by, R'(t) = root3 10t4 ti su, Rate or retension after 5 weeks is giren by, - R'C5) 600 (5) Here you have 1005)4+1 commitend mistake by writing -Go =) R$5) = -600(125) instead of - 600 100625) +1 - 75000 - 75000 6250 +1 6281 =-11.9980 EP-12 so, Rate or retension after s weeks is 12 J. per week. ie. After 5 weeks the retension is decreasing by 12% per week =) 12'(5)