Chapter ISG, Problem 6.1.1.4P

a.

To determine

To define variables and write equation. Also state constraint of variables

Answer to Problem 6.1.1.4P

  $x+y=19.5$

Explanation of Solution

Given information:

Cost of aluminium=$0.84/pound

Cost of copper=$3.01/pound

Cost of silver=$19.52/ounce

20 pounds of metal have 2.5% silver.

Calculation:

Let us assume weight of aluminium be $x$ and weight of copper be $y$ .

According to question,

2.5% will silver in purchase,

So,

Amount of silver= $\frac{2.5}{100}\times 20$

Solving,

Amount of silver= 0.5 pounds

Now,

Total purchase of metal=20 pounds

Substituting values,

  $x+y+0.5=20$

Solving equation,

  $x+y=19.5$  -(1)

b.

To determine

To write system of equations

Answer to Problem 6.1.1.4P

System of equations is

  $x+y=3$

  $0.84x+3.01y=40.74$

Constraints are 0.84 and 3.01 for aluminium and copper respectively.

Explanation of Solution

Given information:

Weight of necklace=3 ounces

Cost of necklace=$40.74

Calculation:

Let us assume weight of aluminium be $x$ and weight of copper be $y$ .

According to question,

  $x+y=3$  -(1)

And,

  $0.84x+3.01y=40.74$   -(2)

Constraints are 0.84 and 3.01 for aluminium and copper respectively.