Answer:
75
Step-by-step explanation:
Average needed to get grade C = 70
Average = Total Amount / No of Items.
No of items = 4
therefore Total needed = 70 x 4 = 280
current total score = 66.75 + 66 + 72.25 = 205
the fourth test minimum score = 280 - 205 = 75
This is the number of combinations of 2 from 23
23C2 = 23! / 2! 21!
A quick way to do this is 23*22 / 2 = 253
1.8, Problem 37: A lidless cardboard box is to be made with a volume of 4 m3
. Find the
dimensions of the box that requires the least amount of cardboard.
Solution: If the dimensions of our box are x, y, and z, then we’re seeking to minimize
A(x, y, z) = xy + 2xz + 2yz subject to the constraint that xyz = 4. Our first step is to make
the first function a function of just 2 variables. From xyz = 4, we see z = 4/xy, and if we substitute
this into A(x, y, z), we obtain a new function A(x, y) = xy + 8/y + 8/x. Since we’re optimizing
something, we want to calculate the critical points, which occur when Ax = Ay = 0 or either Ax
or Ay is undefined. If Ax or Ay is undefined, then x = 0 or y = 0, which means xyz = 4 can’t
hold. So, we calculate when Ax = 0 = Ay. Ax = y − 8/x2 = 0 and Ay = x − 8/y2 = 0. From
these, we obtain x
2y = 8 = xy2
. This forces x = y = 2, which forces z = 1. Calculating second
derivatives and applying the second derivative test, we see that (x, y) = (2, 2) is a local minimum
for A(x, y). To show it’s an absolute minimum, first notice that A(x, y) is defined for all choices
of x and y that are positive (if x and y are arbitrarily large, you can still make z REALLY small
so that xyz = 4 still). Therefore, the domain is NOT a closed and bounded region (it’s neither
closed nor bounded), so you can’t apply the Extreme Value Theorem. However, you can salvage
something: observe what happens to A(x, y) as x → 0, as y → 0, as x → ∞, and y → ∞. In each
of these cases, at least one of the variables must go to ∞, meaning that A(x, y) goes to ∞. Thus,
moving away from (2, 2) forces A(x, y) to increase, and so (2, 2) is an absolute minimum for A(x, y).
Answer:
x = 6
Step-by-step explanation:
Givens
There are 3 sides. All are equal to (4x - 3)
Their sum = 63
Formula
3(4x - 3) = 63
Solution
- 3(4x - 3) = 63 Divide by 3
- 12x - 9 = 63 Add 9 to both sides
- 12x = 63 + 9
- 12x = 72 Divide by 12
- x = 72/12
x = 6 Answer
15
Step-by-step explanation:
A negative number being subtracted makes it positive
5 - -10
5+10 =15
