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3 years ago

12

Sarah is planning to spend a week at her friend’s summer house in Miami Beach. All meals will be provided by her friend’s parent

s, but Sarah still needs at least $500 to pay for her airfare and personal expenses for the week. She is selling bracelets and earrings to fund her trip. A graph representing this situation is shown below.

1 answer:

Marina86 [1]3 years ago

7 0

Answer:

Step-by-step explanation:

500

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There are 45 cards in a card game deck. How many cards in 4 decks?

Alex_Xolod [135]

Answer:

180 cards

Step-by-step explanation:

45x 4= 180

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2 years ago

Daisy is going 12 mph and Sally is going 8 mph if they where 60 miles apart how many hours would it take for them to meet up

abruzzese [7]

Answer:

3 hours

Step-by-step explanation:

we know that

The speed is equal to divide the distance by the time

Let

s ----> the speed in mph

d -----> the distance in miles

t ----> the time in hours

x ----> distance traveled by Daisy to the meeting point

60-x ----> distance traveled by Sally to the meeting point

so

$s=\frac{d}{t}$

Solve for d

$d=st$

<em>Distance traveled by Daisy to the meeting point</em>

$d=st$

we have

$d=x\ mi\\s=12\ mph$

substitute

$x=12t$ ----> equation A

<em>Distance traveled by Sally to the meeting point</em>

$d=st$

we have

$d=(60-x)\ mi\\s=8\ mph$

substitute

$60-x=8t$ ----> equation B

substitute equation A in equation B

$60-12t=8t$

solve for t

$12t+8t=60\\20t=60\\t=3\ hours$

7 0

3 years ago

The reciprocal of 6 4/5 is

kondor19780726 [428]

It should be 34/5*. If you create an improper fraction out of the original one, then creating the reciprocal will be easier.

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4 years ago

Read 2 more answers

A hot metal bar is submerged in a large reservoir of water whose temperature is 60°F. The temperature of the bar 20 s after subm

True [87]

Answer:

A) cooling constant = 0.0101365

B) $\frac{df}{dt} = k ( 60 - F )$

c) F(t) = 60 + 77.46 $e^{0.0101365t}$

D)137.46 ⁰

Step-by-step explanation:

water temperature = 60⁰F

temperature of Bar after 20 seconds = 120⁰F

temperature of Bar after 60 seconds = 100⁰F

A) Determine the cooling constant K

The newton's law of cooling is given as

= $\frac{df}{dt} = k(60 - F)$

= ∫ $\frac{df}{dt}$ = ∫ k(60 - F)

= ∫ $\frac{df}{60 - F}$ = ∫ kdt

= In (60 -F) = -kt - c

60 - F = $e^{-kt-c}$

60 - F = $C_{1} e^{-kt}$ ( note : $e^{-c}$ is a constant )

after 20 seconds

$C_{1}e^{-k(20)}$ = 60 - 120 = -60

therefore $C_{1} = \frac{-60}{e^{-20k} }$ ------- equation 1

after 60 seconds

$C_{1} e^{-k(60)}$ = 60 - 100 = - 40

therefore $C_{1} = \frac{-40}{e^{-60k} }$ -------- equation 2

solve equation 1 and equation 2 simultaneously

= $\frac{-60}{e^{-20k} }$ = $\frac{-40}{e^{-60k} }$

= 6 $e^{20k}$ = 4 $e^{60k}$

= $\frac{6}{4} e^{40k}$ = In(6/4) = 40k

cooling constant (k) = In(6/4) / 40 = 0.40546 / 40 = 0.0101365

B) what is the differential equation satisfied

substituting the value of k into the newtons law of cooling)

60 - F = $C_{1} e^{0.0101365(t)}$

F(t) = 60 - $C_{1} e^{0.0101365(t)}$

The differential equation that the temperature F(t) of the bar

$\frac{df}{dt} = k ( 60 - F )$

C) The formula for F(t)

t = 20 , F = 120

F(t ) = 60 - $C_{1} e^{0.0101365(t)}$

120 = 60 - $C_{1} e^{0.0101365(t)}$

$C_{1} e^{0.0101365(20)}$ = 60

$C_{1} = 60 * 1.291$ = 77.46

C1 = - 77.46⁰ as the temperature is decreasing

The formula for f(t)

= F(t) = 60 + 77.46 $e^{0.0101365t}$

D) Temperature of the bar at the moment it is submerged

F(0) = 60 + 77.46 $e^{0.01013659(0)}$

F(0) = 60 + 77.46(1)

= 137.46⁰

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4 years ago

HELP PLEASE LOTS OF POINTS!!

masha68 [24]

Answer:

890.625

Step-by-step explanation:

2.5x2.5x2.5 (Volume of Cube)=15.625

Density is 57

57=x/15.625

890.625=x

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2 years ago