Answer:
The probability that a randomly chosen light bulb will last less than 900 hours is 0.1587.
Step-by-step explanation:
The life span of these light bulbs is normally distributed with a mean of 1000 hours and a standard deviation of 100 hours
Mean = 
Standard deviation =
We are supposed to find the probability that a randomly chosen light bulb will last less than 900 hours.i.e. P(x<900)
So, 

Z=-1
P(x<900)=P(z<-1)=0.1587
Hence the probability that a randomly chosen light bulb will last less than 900 hours is 0.1587.
Answer:

Step-by-step explanation:
we have

solve for x
Multiply in cross

Divide by 7 both sides

Adds 1 both sides


Rewrite

Answer:
1. 3 2
/5
2. 2/
3
3. 3/4
Step-by-step explanation:
Answer:the answer is six
Step-by-step explanation: