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Leni [432]
3 years ago
14

A team of three students are working on a language-learning app; they need to develop 300 micro-lessons and 300 micro-tests befo

re they can make their first release. Jordan can develop 10 lessons and 5 tests in a day; Marco can develop 5 lessons and 10 tests in a day; Junyi can develop 5 lessons and 8 tests in a day.
(a) Write a system of equations that can be used to determine how long each team member must work to develop exactly 300 lessons and 300 tests.
(b) Find the general solution to the system from (a).
(c) Find the specific solutions if
(i) Junyi gets sick, so can not work;
(ii) Jordan gets a part-time job, and so can only work 10 hours.
Mathematics
1 answer:
Olegator [25]3 years ago
4 0

Answer: a) 15 b)

Step-by-step explanation:

Let X be the number of days:

a)

For LESSONS:

Jordan does 10 / day ( 10*X)

Marco 5 / day ( 5*X)

Junyi 5 / day ( 5*X)

For TESTS:

Jordan does 5 / day ( 5*X)

Marco 10 / day ( 10*X)

Junyi 8 / day ( 8*X)

for each they need a total of 300

a) 10X+5X+5X=300 => 20X = 300 => X = 15 days for the lessons

b) 5X+10X+8X = 300 => 23X = 300 => X = 13.04 days for the tests

so they need 15 days to finish both tasks

now if Junyi gets sick we just eliminate his contribution

a) 10X+5X=300 => 15X = 300 => X = 20 days for the lessons

b) 5X+10X = 300 => 15X = 300 => X = 20 days for the tests

so in 20 days they will finish without him

If jordan works 10 hours a day, we just replace him with 10/24

a) 10(10/24)+5X+5X= 300 => X = 29.58 days for the lessons

b) 5(10/24)+10X+8X = 300 => X = 16.51 days for the tests

so at the end to complete both tasks they need 29.58 days

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R = 850 cm, s = 250 cm and t=940 cm. Find the measure of ZS tothe nearest 10th of a degree
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To find the measure of the s angle que are going use the cosine law because we know all the sides of the triangule:

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The plane x+y+2z=8 intersects the paraboloid z=x2+y2 in an ellipse. Find the points on this ellipse that are nearest to and fart
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Answer:

The minimum distance of   √((195-19√33)/8)  occurs at  ((-1+√33)/4; (-1+√33)/4; (17-√33)/4)  and the maximum distance of  √((195+19√33)/8)  occurs at (-(1+√33)/4; - (1+√33)/4; (17+√33)/4)

Step-by-step explanation:

Here, the two constraints are

g (x, y, z) = x + y + 2z − 8  

and  

h (x, y, z) = x ² + y² − z.

Any critical  point that we find during the Lagrange multiplier process will satisfy both of these constraints, so we  actually don’t need to find an explicit equation for the ellipse that is their intersection.

Suppose that (x, y, z) is any point that satisfies both of the constraints (and hence is on the ellipse.)

Then the distance from (x, y, z) to the origin is given by

√((x − 0)² + (y − 0)² + (z − 0)² ).

This expression (and its partial derivatives) would be cumbersome to work with, so we will find the the extrema  of the square of the distance. Thus, our objective function is

f(x, y, z) = x ² + y ² + z ²

and

∇f = (2x, 2y, 2z )

λ∇g = (λ, λ, 2λ)

µ∇h = (2µx, 2µy, −µ)

Thus the system we need to solve for (x, y, z) is

                           2x = λ + 2µx                         (1)

                           2y = λ + 2µy                       (2)

                           2z = 2λ − µ                          (3)

                           x + y + 2z = 8                      (4)

                           x ² + y ² − z = 0                     (5)

Subtracting (2) from (1) and factoring gives

                     2 (x − y) = 2µ (x − y)

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                            x + y − 9 = 0

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x =  (-1+√33)/4

and

x = -(1+√33)/4.

Further substitution yeilds the critical points  

((-1+√33)/4; (-1+√33)/4; (17-√33)/4)   and

(-(1+√33)/4; - (1+√33)/4; (17+√33)/4).

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f((-1+√33)/4; (-1+√33)/4; (17-√33)/4) = (195-19√33)/8

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