Answer:
- P(≥1 working) = 0.9936
- She raises her odds of completing the exam without failure by a factor of 13.5, from 11.5 : 1 to 155.25 : 1.
Step-by-step explanation:
1. Assuming the failure is in the calculator, not the operator, and the failures are independent, the probability of finishing with at least one working calculator is the complement of the probability that both will fail. That is ...
... P(≥1 working) = 1 - P(both fail) = 1 - P(fail)² = 1 - (1 - 0.92)² = 0.9936
2. The odds in favor of finishing an exam starting with only one calculator are 0.92 : 0.08 = 11.5 : 1.
If two calculators are brought to the exam, the odds in favor of at least one working calculator are 0.9936 : 0.0064 = 155.25 : 1.
This odds ratio is 155.25/11.5 = 13.5 times as good as the odds with only one calculator.
_____
My assessment is that there is significant gain from bringing a backup. (Personally, I might investigate why the probability of failure is so high. I have not had such bad luck with calculators, which makes me wonder if operator error is involved.)
The answer is 7/8. 1/4 x 3 1/2 = 7/8
50 dogs and 10 cats
This creates a 5:1 ratio and allows there to be 40 more dogs than cats. 50-10 equals 40
Answer:
The terms in sequence 2 are half as large as the terms in sequence 1.
Write the hours as ratio
Carrie : Jerry
2 : 5
Put this ratio in words, we say 'for every two hours Carrie takes to inspect a case, Jerry would need 5 hours'
Carrie has done 30 minutes on a case before taking a break. It means Carrie has 1.5 hours left on the case if she was to continue it.
We need to work out the proportion of the time Jerry would take in comparison to 1.5 hours that Carrie would have taken.
First, we divide 2 by 1.5 ⇒

Then we divide 5 by 4/3 ⇒

hours
Jerry would have taken 3.75 hours to finish the rest of the case