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sweet-ann [11.9K]
3 years ago
6

Sandra is showing her work in simplifying (3.3 − 4.2) − 2.8 + 5.7. Identify any error in her work or reasoning. Step 1: (3.3 − 4

.2) − 2.8 + 5.7 Step 2: 3.3 + (− 4.2 − 2.8) + 5.7 (distributive property) Step 3: 3.3 − 7 + 5.7 Step 4: 3.3 + 5.7 − 7 (commutative property) Step 5: 9 − 7 = 2
Mathematics
2 answers:
julsineya [31]3 years ago
8 0
The answer is correct 
but I think in step 2 that should read the Associative property
Mariana [72]3 years ago
3 0

Answer:

Sandra makes an error in second step reasoning .

Step-by-step explanation:

We are given that Sandra is showing her work in simplifying

(3.3-4.2)-2.8+5.7

We have to find the error in her work or reasoning.

Step 1:(3.3-4.2)-2.8+5.7

Step 2:3.3+(-4.2)-2.8)+5.7

Reason: Associative property

Step 3:3.3-7+5.7

Step 4:3.3+5.7-7

Reason: Commutative property

Step 5:9-7=2

Hence, Sandra makes an error in second step reasoning .

Sandra uses distributive property instead of associative property in step 2.

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For each disk drive, there are only two possible outcomes. Either it works, or it does not. The disks are independent. So we use the binomial probability distribution to solve this question.

Binomial probability distribution

The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

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In which C_{n,x} is the number of different combinations of x objects from a set of n elements, given by the following formula.

C_{n,x} = \frac{n!}{x!(n-x)!}

And p is the probability of X happening.

4​% rate of disk drive failure in a year.

This means that 96% work correctly, p = 0.96

a. If all your computer data is stored on a hard disk drive with a copy stored on a second hard disk​ drive, what is the probability that during a​ year, you can avoid catastrophe with at least one working​ drive?

This is P(X \ geq 1) when n = 2

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P(X = 0) = C_{2,0}.(0.96)^{0}.(0.04)^{2} = 0.0016

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99.84% probability that during a​ year, you can avoid catastrophe with at least one working​ drive

b. If copies of all your computer data are stored on four independent hard disk​ drives, what is the probability that during a​ year, you can avoid catastrophe with at least one working​ drive?

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