# Thread: I need fast HELP

1. ## I need help with these fast HELP!!!!!

amount of natural gas is proportional to oxygen consumed. 24.0 kg of Oxygen is
consumed in burning 15 kg of gas how much air 23% oxygen by wieght is consumed to burn 50 kg

a.80 kg
b 345 kg
c. 31.3 kg
d. 135 kg

4.Which of the following expressions would help estimate the value of:
Which of the following expressions would help estimate the value of:
[IMG]

a.36
b.29.25
c.t
d.43

5.During each microsecond the current in an electric circuit decreases by 9.3%. If the initial current is 2.45 mA, what will the current be after 22 microseconds?

0.286 mA
0.496 mA
0.121 mA
1.24 mA

7.The sales S of a product as a function of the time t (in weeks) is given by S = [2300 (5t + 1)]/(2t + 5). Find the instantaneous rate of change of S with respect to t for t = 9 weeks.

125
51
900
100

2. 2. y= 5x^2 sqrt (x+1) find dx/dy
Product rule,
$y'=(5x^2)'\sqrt{x+1}+(5x^2)(\sqrt{x+1})'$
Thus,
$y'=10x\sqrt{x+1}+\frac{5x^2}{2\sqrt{x+1}}$
Thus,
$y'=5x\sqrt{x+1}\left(2+\frac{x}{2(x+1)} \right)$
6.
Find the slope of the tangent to the curve of y = ln (25x + 3) at x = 2.

a.0.47
b.0.50
c.1.2
d.2.5
$y'=\frac{25}{25x+3}$---> By chain rule,
At $x=2$
$y'=\frac{25}{25(2)+3}$
Thus,
$y'\approx .47$

8.Find the center and radius of the circle: x2 + y2 - 18y = -17

Center = (9,0), r = - 8
Center = (1,8), r = 9
Center = (8,1), r =9
Center = (0,9), r = 8
You need to "complete-the-square".
$x^2+(y^2-18y+81)-81=-17$
Thus,
$(x-0)^2+(y-9)^2=64=8^2$
Thus,
$\mbox{center }=(0,9)$
$\mbox{radius }=8$

3. #3. $F(x)=kx$

$25=(20-10)k$

$k=\frac{5}{2}$

$\int_{0}^{5}\frac{5}{2}xdx$

4. Originally Posted by jaycas21
amount of natural gas is proportional to oxygen consumed. 24.0 kg of Oxygen is
consumed in burning 15 kg of gas how much air 23% oxygen by wieght is consumed to burn 50 kg

a.80 kg
b 345 kg
c. 31.3 kg
d. 135 kg

4.Which of the following expressions would help estimate the value of:
Which of the following expressions would help estimate the value of:
[IMG]

a.36
b.29.25
c.t
d.43

5.During each microsecond the current in an electric circuit decreases by 9.3%. If the initial current is 2.45 mA, what will the current be after 22 microseconds?

0.286 mA
0.496 mA
0.121 mA
1.24 mA

7.The sales S of a product as a function of the time t (in weeks) is given by S = [2300 (5t + 1)]/(2t + 5). Find the instantaneous rate of change of S with respect to t for t = 9 weeks.

125
51
900
100
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RonL