Alice is making a gold necklace. The length of the chain is

You were sick and take a test a day late. Your 95 raised the class average from 69 to 70. How many students, including you, took

tia_tia [17]

Answer:

26

Explanation:

The average is the mean. It is calculated adding all the values and dividing the sum by the number of values (data):

For the students who took the test the day before you, you can write:

$mean_1=\sum scores/n$

Where n is the number of students who took the test first.

Thus, when the average was 69 the equation is:

$69=\sum scores/n$

When you take the test, the n + 1, the new average is 70, and the sum of the scores raised in 95 points:

$mean_2=(\sum scores + 95)/(n+1)\\ \\ 70=(\sum scores+95)/(n+1)$

Now you have a system of two equation and two unknowns, so you can solve it.

Clear the sum of the scores from the first equation:

$69=\sum scores/n=>\sum scores=69n$

Subsitute in the second equation:

$70=(69n+95)/(n+1)$

Solve for n:

$70(n+1)=69n+95\\ \\ 70n+70=69n+95\\ \\ 70n-69n=95-70\\ \\ n=25$

Thus, when you include your self the number of students who took the test was 25 + 1 = 26.

5 0

3 years ago

The Dalton’s completed 20% of their 2170 mile tripe the first day- how many miles did they travel the first day? How many miles

Alenkinab [10]

20% of 2170 miles is 434.

3 0

3 years ago

Write an equation of a line that is perpendicular to y = 2/3 x + 8 and has a y-intercept of

Otrada [13]

Answer:

y = -3/2x + 2

Step-by-step explanation:

Since you know it has a point at (0, 2) - the y intercept, put those values into the equation and solve. To be perpendicular it seems the reciprocal of the slope with the opposite sign, so 2/3 is the original slope, and -3/2 becomes the new slope.

y = 2/3x + 8 becomes

2 = -3/2(0) + b We substitute in the x and y values, but we have to figure out what the last number will be.

2 = 0 + b

b = 2

So put the whole equation together

y = -3/2x + 2

3 0

2 years ago

In 1980, Ric was twice as old as Nancy who was as old as Manual. In 1992, Ric, Nancy and Manual’s ages added up to 78 years. How

myrzilka [38]

He was 21 in 1980,
There are twelve years in between them all so you subtract 36 from 78 and since he was double as old as Nancy, and Manual was the same age as her, you would divide 42 into two parts, Ric and the 10.5 year olds, and Ric would be 21 in 1980.

6 0

3 years ago

I need help with this please!!!

Natasha_Volkova [10]

Answer:

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7 0

3 years ago