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Vaselesa [24]
2 years ago
9

Sara is 9 years younger than her brother, Michael. The sum of their ages is 47 years. How old is Sara and how old is her brother

, Michael?
Mathematics
1 answer:
kotykmax [81]2 years ago
7 0

Answer:

Michael is 38 and Sara is 29

Step-by-step explanation:

Because it says the sum of their age is 47 you do 47-9=38 so that would be Michael's age and than because Sara is 9 years younger than him and then you would do 38-9=29

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Answer:I think it would be $9

Step-by-step explanation:

50% of 20 is $10

10% of $10 is $1

Subtract 1 from 10, which gives you $9

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What is the general form of the equation for the given circle centered at o (0,0) (4,5)?
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Which of the following are solutions to the system graphed below.
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Weird. I think you just need to look if the point falls on the shaded area. But only (-5,5) does ...

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3 years ago
An object is heated to 100°. It is left to cool in a room that
stepladder [879]

Answer:

Step-by-step explanation:

Use Newton's Law of Cooling for this one.  It involves natural logs and being able to solve equations that require natural logs.  The formula is as follows:

T(t)=T_{1}+(T_{0}-T_{1})e^{kt} where

T(t) is the temp at time t

T₁ is the enviornmental temp

T₀ is the initial temp

k is the cooling constant which is different for everything, and

t is the time (here, it's in minutes)

If we are looking first for the temp after 20 minutes, we have to solve for the k value.  That's what we will do first, given the info that we have:

T(t) = 80

T₁ = 30

T₀ = 100

t = 5

k = ?

Filling in to solve for k:

80=30+(100-30)e^{5k} which simplifies to

50=70e^{5k} Divide both sides by 70 to get

\frac{50}{70}=e^{5k} and take the natural log of both sides:

ln(\frac{5}{7})=ln(e^{5k})

Since you're learning logs, I'm assuming that you know that a natural log and Euler's number, e, "undo" each other (just like taking the square root of something squared).  That gives us:

-.3364722366=5k

Divide both sides by 5 to get that

k = -.0672944473

Now that we have a value for k, we can sub that in to solve for T(20):

T(20)=30+(100-30)e^{-.0672944473(20)} which simplifies to

T(20)=30+70e^{-1.345888946}

On your calculator, raise e to that power and multiply that number by 70:

T(20)= 30 + 70(.260308205) and

T(20) = 30 + 18.22157435 so

T(20) = 48.2°

Now we can use that k value to find out when (time) the temp of the object cools to 35°:

T(t) = 35

T₁ = 30

T₀ = 100

k = -.0672944473

t = ?

35=30+100-30)e^{-.0672944473t} which simplifies to

5=70e^{-.0672944473t}

Now divide both sides by 70 and take the natural log of both sides:

ln(\frac{5}{70})=ln(e^{-.0672944473t}) which simplifies to

-2.63905733 = -.0672944473t

Divide to get

t = 39.2 minutes

3 0
3 years ago
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wariber [46]

Answer:

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Step-by-step explanation:

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The slope is m and the point is (x1,y1)

y - -3 = 1/2(x -4)

y+3 = 1/2 (x-4)

5 0
2 years ago
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