(20 points)

If x = 7 and f = 4 and g = 9 and l = 24 and p = 12 and e = 9847493 then what is x ÷ fg X i ÷ p

REY [17]

0.38^• or 7/18. If the x after the g and before the i is a multiplication (btw the ^• is a repeater

3 0

2 years ago

A 200-gal tank contains 100 gal of pure water. At time t = 0, a salt-water solution containing 0.5 lb/gal of salt enters the tan

Artyom0805 [142]

Answer:

1) $\frac{dy}{dt}=2.5-\frac{3y}{2t+100}$

2) $y(t)=(50+t)- \frac{12500\sqrt{2} }{(50+t)^{\frac{3}{2} }}$

3) 98.23lbs

4) The salt concentration will increase without bound.

Step-by-step explanation:

1) Let $y$ represent the amount of salt in the tank at time t, where t is given in minutes.

Recall that: $\frac{dy}{dt}=rate\:in-rate\:out$

The amount coming in is $0.5\frac{lb}{gal}\times 5\frac{gal}{min}=2.5\frac{lb}{min}$

The rate going out depends on the concentration of salt in the tank at time t.

If there is $y(t)$ pounds of salt and there are $100+2t$ gallons at time t, then the concentration is: $\frac{y(t)}{2t+100}$

The rate of liquid leaving is is 3gal\min, so rate out is $=\frac{3y(t)}{2t+100}$

The required differential equation becomes:

$\frac{dy}{dt}=2.5-\frac{3y}{2t+100}$

2) We rewrite to obtain:

$\frac{dy}{dt}+\frac{3}{2t+100}y=2.5$

We multiply through by the integrating factor: $e^{\int \frac{3}{2t+100}dt }=e^{\frac{3}{2} \int \frac{1}{t+50}dt }=(50+t)^{\frac{3}{2} }$

to get:

$(50+t)^{\frac{3}{2} }\frac{dy}{dt}+(50+t)^{\frac{3}{2} }\cdot \frac{3}{2t+100}y=2.5(50+t)^{\frac{3}{2} }$

This gives us:

$((50+t)^{\frac{3}{2} }y)'=2.5(50+t)^{\frac{3}{2} }$

We integrate both sides with respect to t to get:

$(50+t)^{\frac{3}{2} }y=(50+t)^{\frac{5}{2} }+ C$

Multiply through by: $(50+t)^{-\frac{3}{2}}$ to get:

$y=(50+t)^{\frac{5}{2} }(50+t)^{-\frac{3}{2} }+ C(50+t)^{-\frac{3}{2} }$

$y(t)=(50+t)+ \frac{C}{(50+t)^{\frac{3}{2} }}$

We apply the initial condition: $y(0)=0$

$0=(50+0)+ \frac{C}{(50+0)^{\frac{3}{2} }}$

$C=-12500\sqrt{2}$

The amount of salt in the tank at time t is:

$y(t)=(50+t)- \frac{12500\sqrt{2} }{(50+t)^{\frac{3}{2} }}$

3) The tank will be full after 50 mins.

We put t=50 to find how pounds of salt it will contain:

$y(50)=(50+50)- \frac{12500\sqrt{2} }{(50+50)^{\frac{3}{2} }}$

$y(50)=98.23$

There will be 98.23 pounds of salt.

4) The limiting concentration of salt is given by:

$\lim_{t \to \infty}y(t)={ \lim_{t \to \infty} ( (50+t)- \frac{12500\sqrt{2} }{(50+t)^{\frac{3}{2} }})$

As $t\to \infty$ , $50+t\to \infty$ and $\frac{12500\sqrt{2} }{(50+t)^{\frac{3}{2} }}\to 0$

This implies that:

$\lim_{t \to \infty}y(t)=\infty- 0=\infty$

If the tank had infinity capacity, there will be absolutely high(infinite) concentration of salt.

The salt concentration will increase without bound.

6 0

2 years ago

Two balls are pulled one after another, without replacement, from the box containing three black, five yellow, and seven red bal

kolezko [41]

Answer:

1/14

Step-by-step explanation:

5/15 × 3/14 = 1/14

Or 0.0714 (3sf)

6 0

2 years ago

In June, Meg runs a race 10 seconds faster than she did in April. Let y represent her finishing time for the race in April. Whic

Marina CMI [18]

Answer: The expression that represents Meg's finishing time in June is "y - 10".

The problem started with Meg running in April. She had a time in April and we called it "y".

Now, Meg ran again in June. In June, she did 10 seconds faster. So it makes since that we need to subtract 10 from her April time, "y". Therefore, the expression is simply "y - 10".

8 0

2 years ago

The perimeter of a playing field for a certain sport is 254 ft. The length is 47 ft longer than the width. Find the dimensions.

Vikentia [17]

Answer: the length is 87 feet

The width is 40 feet

Step-by-step explanation:

Let L represent the length of the playing field.

Let W represent the width of the playing field.

The playing field is rectangular. The formula for determining the perimeter of a rectangle is expressed as

Perimeter = 2(L + W)

The perimeter of a playing field for a certain sport is 254 ft. This means that

254 = 2(L + W)

L + W = 254/2

L + W = 127 - - - - - - - - - - - -1

The length is 47 ft longer than the width. This means that

L = W + 47

Substituting L = W + 47 into equation 1, it becomes

W + 47 + W = 127

2W + 47 = 127

2W = 127 - 47 = 80

W = 80/2 = 40

L = W + 47 = 40 + 47

L = 87

4 0

2 years ago