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3. A football team is performing badly. The manager of the team can buy some new players to try and gain some extra points.

A very simple model of the manager’s situation is as follows.
He can buy new attackers for £3 million each and new defenders for £1 million each.
Each attacker will help the club to get two more points and each defender will help the club to get one more point.
The manager has £12 million to spend.
The team must gain at least 5 more points.
The manager must buy at least one defender and at least one attacker. He must spend at least £6 million.
The manager buys x attackers and y defenders.

(a) Express the manager’s situation in terms of inequalities suitable for investigating the problem by linear programming.(4)
(b) On the graph below, draw a suitable diagram to enable the problem to be investigated graphically, indicating the feasible region.



This is a question in my summer holiday work and i cant do it, HELP?!?!?!
I'll try and get you started.

The manager buys x attackers and y defenders; you can write down how much that will cost in terms of x & y because you're given the cost of an attacker and of a defender. You also know that his maximum budget is £12M and that the cost that you've just calculated in terms of x and y must be less than that £12M. This gives you the first inequality. Can you see now how to get the second inequality?
Reply 2
Original post by Gregorius
I'll try and get you started.

The manager buys x attackers and y defenders; you can write down how much that will cost in terms of x & y because you're given the cost of an attacker and of a defender. You also know that his maximum budget is £12M and that the cost that you've just calculated in terms of x and y must be less than that £12M. This gives you the first inequality. Can you see now how to get the second inequality?




So would one be: x+y<12m
And the second: x+3y >(or equal to) 6m

Thanks for your help!,
Original post by paigeemily
So would one be: x+y<12m
And the second: x+3y >(or equal to) 6m

Thanks for your help!,


Not quite. Let's take the first inequality: he buys x attackers and y defenders and the total cost must be less that £12M. An attacker costs £3M, therefore x attackers must cost x times £3M. A defender costs £1M therefore y defenders costs y times £1M. The sum of these two costs must be less than £12M. You can then simplify the inequality by dividing though by a million!

The second inequality comes from the number of points required.
Reply 4
Original post by Gregorius
Not quite. Let's take the first inequality: he buys x attackers and y defenders and the total cost must be less that £12M. An attacker costs £3M, therefore x attackers must cost x times £3M. A defender costs £1M therefore y defenders costs y times £1M. The sum of these two costs must be less than £12M. You can then simplify the inequality by dividing though by a million!

The second inequality comes from the number of points required.



Okay, so that makes 3x + y < 12m ?

And do you have to relate that to points or is a whole anew iequality?
Original post by paigeemily
Okay, so that makes 3x + y < 12m ?

And do you have to relate that to points or is a whole anew iequality?


That's nearly it. Dividing out the million gives you 12 on the right hand side and also, since the manager has up to and including 12M to spend it should be 3x + y <= 12.

The points requirement gives you a second inequality that has hold simultaneously with the first.

For the second part of the question, plot the line 3x + y = 12 and the line corresponding to the second inequality and think about how the plane is divided up by these lines.
Reply 6
Original post by Gregorius
That's nearly it. Dividing out the million gives you 12 on the right hand side and also, since the manager has up to and including 12M to spend it should be 3x + y <= 12.

The points requirement gives you a second inequality that has hold simultaneously with the first.

For the second part of the question, plot the line 3x + y = 12 and the line corresponding to the second inequality and think about how the plane is divided up by these lines.


Thank you!
Just would the second one be 2x + y => 5
(edited 8 years ago)
Original post by paigeemily
Thank you!
Just would the second one be 2y + y => 5


2x + y >= 5.
Reply 8
Original post by Gregorius
2x + y >= 5.


Thank you so much for all of your help!
Original post by paigeemily
Thank you so much for all of your help!


No trouble at all.

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