Newton's Law of Cooling
Tf=Ts+(Ti-Ts)e^(-kt) where Tf is temp at time t, Ts is temp of surroundings, Ti is temp of object/fluid. So we need to find k first.
200=68+(210-68)e^(-10k)
132=142e^(-10k)
132/142=e^(-10k)
ln(132/142)=-10k
k=-ln(132/142)/10
k≈0.0073 so
T(t)=68+142e^(-0.0073t) so how long until it reaches 180°?
180=68+142e^(-0.0073t)
112=142e^(-0.0073t)
112/142=e^(-0.0073t)
ln(112/142)=-0.0073t
t= -ln(112/142)/(0.0073)
t≈32.51 minutes
Answer: speed is 540 km/h
Step-by-step explanation: Lets mark speed as v.
Because distenace is same, you can mark 6 h · 900 km/h = 10 h · v
and v = 5400 km / 10 h = 540 km/h.
Or using inverse proportions : 10 h / 6 h = v / 900 km/h .
Before multiplying you turn lastproportion around :
10 h / 6 h = 600 km/ h / v ,which gives 10 v = 6 · 900 km/h
and result is same
Answer:
See below
Step-by-step explanation:
r/6 <-6 multiply both sides by 6 to get
<u>r < - 36 </u>
<u />
<u> or</u> 4r+2 > 18 subtract 2 from both sides of the equation
4r > 16 divide both sides by 4
<u> r > 4 </u>
