A-Level Maths: F7-06 [Exponential Growth & Decay: The Dosage Problem]

[georgeloffhagen]

Hi thanks for the videos! Could you just treat the 2nd dose as one dose of 10mg+5.353mg still in the blood stream from the first dose in the part (b) and (c). I try the questions before watching the video and that was my method, the answers were the same, but would this not get me marks for working out. Sorry for asking so long after the upload date.

[sophiekelly]

When you’ve factorised shouldn’t the bit it the bracket be (1+1+e^-5/8) because you’ve got two e^-5/8?Or am I being I compete idiot😂

[hisschoolwork]

Hi Jack, for part (c), after diving by 10 to get 0.3=e^-1/8+e^-1/8(t+5), could you not take the natural logarithm of all terms, simplifying to ln(0.3)=-1/8t-1/8(t+5), and further to ln(0.3)=-1/8t-1/8t-5/8, then after adding the 5/8 to the other side, and dividing by (-1/8 - 1/8), leaving t on it's own, how come the answer doesn't come to 13.1 hours as you did? Sorry for the hassle, thanks Jack

[haleemahijazi]

For part c my calculator is giving 1.44.. as the answer, even though I am using same values as you. Would you know why this is?