An electronics retailer offers an optional protection plan for a mobile phone it sells. Customers can choose

Mathematics

2 answers:

Darina [25.2K]2 years ago

8 0

Answer:

$79

Step-by-step explanation:

That's the Khan Academy answer

Oxana [17]2 years ago

4 0

Answer:

79$ / 0.14

Step-by-step explanation:

Depending on the khan academy question the answer may differ between the two. Make sure to read your example closely. If it asks for dollars 79 is your answer if not go for 0.14. <3

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iVinArrow [24]

Answer:

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2 years ago

Radium 226 has a decay rate that satisfies the differential equation D'(t)= -.00043D(t). Assume that D(0)=100.

Rus_ich [418]

Answer:

A) $D(t)=100e^{-0.00043t}$

B) ${D(t=100)}=95.8$

C) τ=2326 years

Step-by-step explanation:

Consider the differential equation:

$\frac{dD}{dt}=-0.00043D$

Separate variables dD and dt:

$\frac{dD}{D}=-0.00043dt$

Integrate: Remember that The integral of dD/D is ln(D).

$\int\limits^{D}_{D_0} {\frac{1}{D} } \, dD=\int\limits^{t}_{0} {-0.00043} \, dt$

$ln(\frac{D}{D_0})=-0.00043t\\\frac{D}{D_0}=e^{-0.00043t}$

$D=D_0*e^{-0.00043t}$

And do $D_0=100$ , so:

$D=100*e^{-0.00043t}$

The function we have found is a function that let us know how many of Ra is after t years, so, evaluate the function at t=100:

$D(t=100)=100*e^{-0.00043*100}=95.791\\$

Which rounded is 95.8.

C) For this equation it is known that the life half life τ is equal to (1/λ), where λ is the exponential number that is multiplying to -t in the D(t) function; so for this case, λ=0.00043, and the life half life is $\frac{1}{0.00043}=2325.58$ ,