3 years ago

SECUL

1 answer:

4 0

Answer:
he bought 5 english books and 5 math books

explanation:
total spent on english books 5x22=110
total spent on math books 5x29=145
total spent together: $255

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morpeh [17]

Answer:

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Step-by-step explanation:

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7 0

3 years ago

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A welder drops a piece of red-hot steel on the floor. The initial temperature of the steel is 2,500 degrees Fahrenheit. The ambi

sergey [27]

Answer: After 18.05 minutes, the temperature of steel becomes 100 degrees.

Step-by-step explanation:

Since we have given that

Initial temperature = 2500

At t = 0,

we get that

$f(t)=Ce^{-kt}+80\\\\2500=C+80\\\\2500-80=C\\\\2420=C$

After 2 minutes, the temperature of the steel is 1500 degrees.

so, it becomes,

$1500=2420e^{-2k}+80\\\\1500-80=2420e^{-2k}\\\\\dfrac{1420}{2420}=e^{-2k}\\\\0.587=e^{-2k}\\\\\ln 0.587=-2k\\\\-0.533=-2k\\\\k=\dfrac{0.533}{2}\\\\k=0.266$

So, We need to find the number of minutes when the temperature of steel would be 100 degrees.

So, it becomes,

$100=2420e^{-0.266t}+80\\\\100-80=2420e^{-0.266t}\\\\20=2420e^{-0.266t}\\\\\dfrac{20}{2420}=e^{-0.266t}\\\\\ln \dfrac{20}{2420}=-0.266t\\\\-4.8=-0.266t\\\\t=\dfrac{4.8}{0.266}\\\\t=18.05$