12%=(3+10%*x)/(20+x)
x=30
add 30 pounds of the second alloy
Answer:
(4) 29, 33, 37
(6) 53, 59, 65
(5) -16, -20, -24
Step-by-step explanation:
We have the frequencies for each of the grades. We can estimate the number of students graded by adding all those frequencies. Let's call N the total number of grades:
We have then a total number of grades of 39.
The corresponding relative frequency for a grade is the ratio of the frequency to the total number of "samples", 39 in this case.
Then, for grade A, the relative frequency (RF) will be:
This will be the fraction of the total grades that are A. Represented as a percentage will be 10.26%, rounded to two decimal places.
Now, to complete the table we do the same for the other frequencies:
For grade B:
For grade C:
For grade D:
For grade F:
Answer:
(x + 7)^2 = 64
Step-by-step explanation:
x^2 + 23x – 19 = 9x - 4
x^2 + 23x - 9x = -4 + 19
x^2 + 14x = 15 = 0
Completing the square:
(x + 14/2)^2 - (14/2)^2 = 15
(x + 7)^2 - 49 = 15
(x + 7)^2 = 64
Using a system of equations, it is found that there are 5 dimes and 9 quarters in his pocket.
<h3>What is a system of equations?</h3>
A system of equations is when two or more variables are related, and equations are built to find the values of each variable.
In this problem, the variables are given as follows:
- Variable x: number of dimes in his pocket.
- Variable y: number of quarters in his pocket.
He has a total of 14 coins, hence:
x + y = 14 -> y = 14 - x.
They are worth $2.75, hence, considering the value of each coin(dimes $0.1 and quarters $0.25), we have that:
0.1x + 0.25y = 2.75
Since y = 14 - x:
0.1x + 0.25(14 - x) = 2.75
x = (0.25*14 - 2.75)/0.15.
x = 5.
y = 14 - x = 14 - 5 = 9.
There are 5 dimes and 9 quarters in his pocket.
More can be learned about a system of equations at brainly.com/question/24342899
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