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3 years ago

7

In a test (+4) marks are given for every correct answers and (-3) marks are given for every incorrect answers 1) Tahiya answered

all questions and scored 40 marks though she got 12 correct answers. 2) Helmin also answered all the questions and scored (-14) marks though he got 5 correct answers. How many incorrect answers had they attempted?

1 answer:

stealth61 [152]3 years ago

4 0

Answer:

Tahiya attempted 3 incorrect answers.

Helmin attempted 11 incorrect answers.

Step-by-step explanation:

Correct = +4

Incorrect = -3

1) Tahiya got 12 correct answers and scored a 40, the number of incorrect answers was:

$4*12-3I=40\\I=\frac{8}{3}\\I=2.67$

2) Helmin got 5 correct answers and scored a -14, the number of incorrect answers was:

$4*5-3I=-14\\I=\frac{34}{3}\\I=11.33$

In both cases the number of incorrect answers obtained is a fraction, which means that either the data provided is inaccurate, or that the scores obtained by the students are approximate. Let's round the number of incorrect answers to the nearest whole answer.

Tahiya attempted 3 incorrect answers.

Helmin attempted 11 incorrect answers.

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Answer:

Options A, B and C are correct.

Step-by-step explanation:

Central Limit Theorem

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So the correct options are:

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Answer:

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And we can find this probability with this difference:

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Step-by-step explanation:

Previous concepts

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Where $\mu=5$ and $\sigma=1.2$

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$P(X>3.5)$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

If we apply this formula to our probability we got this:

$P(X>3.5)=P(\frac{X-\mu}{\sigma}>\frac{3.5-\mu}{\sigma})=P(Z>\frac{3.5-5}{1.2})=P(z>-1.25)$

And we can find this probability using the complement rule:

$P(z>-1.25)=1-P(z$

Part b

We are interested on this probability

$P(X$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

If we apply this formula to our probability we got this:

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Part c

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$P(-1.25$

And in order to find these probabilities we can use tables for the normal standard distribution, excel or a calculator.

$P(-1.25$

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