Answer:
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Step-by-step explanation:
Answer:
Cost of the pen = Rs.100
Step-by-step explanation:
Let the marked price = x
When the shopkeeper is selling for x, his gain = Rs. 20
Cost price = Marked price - Gain = x - 20 --------(I)
After discount:
Discount = 10%
Marked price after discount = (100 - 10)% of x = 90% of x
= 0.9 * x = 0.9x
When the shopkeeper is selling for 0.9x, his gain = Rs.8
Cost price = Marked price - gain = 0.9x - 8 -------(II)
From (I) and (II)
x - 20 = 0.9x - 8
x = 0.9x - 8 + 20
x = 0.9x + 12
x - 0.9x = 12
0.1x = 12
x = 12/0.1
x = 120
Marked price of pen = Rs.120
Cost price = 120 - 20
Cost price = Rs. 100
Answer: $14.96
Step-by-step explanation:
13.98 + .98 = 14.96
Given Information:
Number of lithium batteries = n = 16
Mean life of lithium batteries = μ = 645 hours
Standard deviation of lithium batteries = σ = 31 hours
Confidence level = 95%
Required Information:
Confidence Interval = ?
Answer:

Step-by-step explanation:
The confidence interval is given by

Where μ is the mean life of lithium batteries, σ is the standard deviation, n is number of lithium batteries selected, and t is the critical value from the t-table with significance level of
tα/2 = (1 - 0.95) = 0.05/2 = 0.025
and the degree of freedom is
DoF = n - 1 = 16 - 1 = 15
The critical value (tα/2) at 15 DoF is equal to 2.131 (from the t-table)





Therefore, the 95% confidence interval is 628.5 to 661.5 hours
What does it mean?
It means that we are 95% confident that the mean life of 16 lithium batteries is within the interval of (628.5 to 661.5 hours)