Answer: 
Step-by-step explanation:
Multiply by the reciprocal in order to get rid of the fraction in the denominator.
Answer:
612 Hz.
Step-by-step explanation:
The frequency of the sound will be proportionally higher when coming towards you. The increase is related to the speed of the train.
So the frequency will be:
580 + (580 / 343) * 18.8
= 612 Hz.
This is called the Doppler effect.
Answer:
S'(x)=-0.006x2+0.8x+9
Step-by-step explanation:
The rate of change of the sales S(x) with respect to the amount of money spent on advertising x is then the derivative of S(x) with respect to x. What we have to calculate is S'(x).
We know that the derivative of 
is 
(where a is a constant), and the derivative of a sum is the sum of the derivatives, so we can calculate the derivative of each term independently:
S'(x)=(−0.002x3 + 0.4x2 + 9x + 500)'=(−0.002)(3)x2 + (0.4)(2)x + 9
Which means:
S'(x)=-0.006x2+0.8x+9
Answer:
1. y=kx
2. y=60
Step-by-step explanation:
y is directly proportional to x
y=kx
Find Constant K, when y=30 & x=6
Make K the subject of the formula first
K=y/x
K=30/6
k=5
When k is 5, x is 12, find y
y=kx
y=5×12
y=60
Answer:
If the discount is 32%, the new price would be $26.486
Step-by-step explanation:
To get the answer, you would need to multiply 38.95 * .32 which would equal 12.464.
12.464 is the 32% discount
38.95 - 12.464 = 26.486
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