The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes)
1 answer:
Answer and Step-by-step explanation: Suppose remaining credit is y and time in minutes is x. To determine a value of y corresponding to a value of x, first find the equation for the function.
Since the function is linear, the equation is of the form: y = mx + b. To determine it:
1) Find slope, or inclination, of the line:
slope (m) =
where x's and y's are points of the function.
2) Determine the y-intercept, or b: Use a point of the function, replace them at the equation, y = mx + b, and find b.
3) The equation will be: y = mx + b
With the equation, replace x for the minutes the question is asking and calculate to find the remaining credit.
Th result will be a pair (x,y)
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Answer:
(a) 0.119
(b) 0.1699
Solution:
As per the question:
Mean of the emission, million ponds/day
Standard deviation, million ponds/day
Now,
(a) The probability for the water pollution to be at least 15 million pounds/day:
= 1 - P(Z < 1.178)
Using the Z score table:
= 1 - 0.881 = 0.119
The required probability is 0.119
(b) The probability when the water pollution is in between 6.2 and 9.3 million pounds/day:
P(Z < - 0.86) - P(Z < - 1.96)
Now, using teh Z score table:
0.1949 - 0.025 = 0.1699