n Chatty Cathy’s cell phone plan she pays for minutes used plus a fixed monthly charge. For 500 minutes she pays $35 total, and
1 answer:
Answer
Find out the what is her monthly fixed charge .
To prove
Let us assume that the cost per mintues = x
Let us assume that the monthly charge be = y
As given
n Chatty Cathy’s cell phone plan she pays for minutes used plus a fixed monthly charge.
For 500 minutes she pays $35 total
Than the equation becomes
500x + y = 35
As given
for 1500 minutes used she pays $55 total.
Than the equation becomes
1500x + y = 55
Subtracted 500x + y = 35 from 1500x + y = 55
1500x - 500x + y - y = 55 - 35
1000x = 20
x = $0.02
Put in the 500x + y = 35
500 × 0.02 + y = 35
10 + y = 35
y = 35 - 10
y = $25
Therefore the monthly fixed charge be $25.
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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