We can use ratios and the cross-multiply-divide to find this.
The ratio 21:5 is avaliable via the question. We then need to compare that to the ratio x:100, the 100 being the percent and the x being the number of airplane parts.
21/5 = x/100
We can then solve for x to find the number of airplane parts. First we multiply by 100 on both sides to get 2100/5 = x. Therefore x = 420 and there are 420 airplane parts.
The answer is C, mean =100 and standard deviation=15
Answer- (5x-1)(2x+1)
let me know if you need to see work
Answer: (1500.66,1599.34)
Step-by-step explanation:
Confidence interval for population mean:

,where
= Sample mean , n= Sample size, z* = critical two tailed z-value ,
= population standard deviation.
As per given , we have
n= 16
square feet
square feet

Critical z-value = 
Confidence interval for population mean:

Required confidence interval: (1500.66,1599.34)
Sample space = {p, r, o, b, a, b, i, l, I, t, y} = 11 possible outcomes
1sr event: drawing an I ( there are 2 I); P(1st I) = 2/11
2nd event drawing also an i: This is a conditional probability, since one I has already been selected the remaining number of I is now 1, but also the sample space from previously 11 outcome has now 10 outcomes (one letter selected and not replaced)
2nd event : P(also one I) = 1/10
P(selecting one I AND another I) is 2/11 x 1/10
P(selecting one I AND another I) =2/110 = 0.018