You need to understand that you're solving for the average, which you already know: 90. Since you know the values of the first three exams, and you know what your final value needs to be, just set up the problem like you would any time you're averaging something.
Solving for the average is simple:
Add up all of the exam scores and divide that number by the number of exams you took.
(87 + 88 + 92) / 3 = your average if you didn't count that fourth exam.
Since you know you have that fourth exam, just substitute it into the total value as an unknown, X:
(87 + 88 + 92 + X) / 4 = 90
Now you need to solve for X, the unknown:
87
+
88
+
92
+
X
4
(4) = 90 (4)
Multiplying for four on each side cancels out the fraction.
So now you have:
87 + 88 + 92 + X = 360
This can be simplified as:
267 + X = 360
Negating the 267 on each side will isolate the X value, and give you your final answer:
X = 93
Now that you have an answer, ask yourself, "does it make sense?"
I say that it does, because there were two tests that were below average, and one that was just slightly above average. So, it makes sense that you'd want to have a higher-ish test score on the fourth exam.
Answer:
a=28
Step-by-step explanation:
use inverse operations
200 has the same value as 20 tens beucase 20*10=200
Answer:
121
.
The axis of symmetry is the line x= 6
The parabola opens downwards.
The value of h when the equation is in vertex form is positive.
Step-by-step explanation:
In the pictures.
Hope it helps! :)
Answer:
50 of D and 10 of C
Step-by-step explanation:
First of all, put this data into 2 equations.
You sold 60 items, so C+D=60
C is $5 so we can represent it by 5C
D is $7 so we can represent it by 7D
You made $400 total from C and D, so 5C+7D=400
We can use simultaneous equations to solve this.
To eliminate one of these variables, we'll multiply the first one by 5 to make it 5C like the other.
5(C+D=60) (make sure you multiply both sides.)
so 5C+5D=300
5C+7D=400
Now we solve it:
5C-5C+7D-5D=400-300
7D-5D=100
2D=100
D=50
Now we can substitute this with one of the equations to find C
C+50=60
C=60-50
C=10
so, (10x5)+(50x7)=400
