Mrs. Smith's class is working on a variety of science experiments. Each

Mathematics

1 answer:

SVETLANKA909090 [29]3 years ago

8 0

Answer:

Step-by-step explanation:

If there are <em>n</em> students, then the number of pairs is $\frac{n(n-1)}{2}$ .

With 12 students, $\frac{12(12-1)}{2} = \frac{132}{2}=66$ pairs can be formed.

The reason the formula works is this: Each of the 12 students can be paired with 11 other students (no student is paired with him/her self). But counting 12 x 11 = 132 counts each pair <u>twice</u>. Example: student A can be paired with student B,..., student B can be paired with student A. The pair was counted two times.

See the attached image that shows pairings of 5 students. There are

5(5 - 1)/2 = 5(4)/2 = 10 pairs.

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Please help Explanation will be appreciated thanks,

Genrish500 [490]

Answer: A; 6.3%

Step-by-step explanation:

Problem 1

For the first problem, we first want to find y so that we can plug it into the expression.

We can use elimination method for the system of equations to solve.

3x+3y=21

3x-y=5

We subtract both equations to eliminate x.

4y=16 [divide both sides by 4]

y=4

Now that we know y, we can plug it into the expression.

$\frac{4}{2} -3$ [divide]

$2-3$ [subtract]

$-1$

We know that the answer is A.

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Problem 2

For the second problem, we need to know how to calculate percent error. The formula for precent error is $\frac{|measured-exact|}{exact} *100%$ . We know that the exact value is 80 because the buyer was supposed to given 80. 75 is the measured value because that was what the buyer was given.