Question 986046: I really need help with this.
A driving school has 600 trainees. On one particular day, a small group of trainees thought they heard their instructor said that no one one had managed to pass for their advanced driving techniques course. 24 hours later, a survey of the entire student population revealed that by then 40 students had heard this rumour. The rumour spreads according to the equation, R(t)=600/〖1+75e〗^kt where R(t) is the number of trainees who had heard the rumour, t is the time in hours after the first group of trainees though they heard their instructor and k is a constant.
Find the time needed for 90% of the trainee population to have heard the rumour.
Answer by macston(5194)   (Show Source):
You can put this solution on YOUR website! .
I cannot decipher your equation, but the process would be:
Using 40 for R(t) and 24 hrs for t, find k.
.
R(t)=600/〖1+75e〗^24k
40-600/〖1=75e〗^24k
(40-600/〖1)/(75〗)=e^24k
ln((40-600/〖1)/(75〗))=ln(e^24k)
ln((40-600/〖1)/(75〗))=24k
(ln((40-600/〖1)/(75〗)))/24=k
.
Then using (0.90)(600)=540 for R(t) and the value of k from above, solve for t.
.
If you can clarify your equation, I can offer more help.
I noticed you re-posted the same garbled equation again, perhaps someone else can help you.
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