Section 12: Calculating with Matrices 157

 

 

Week

 

 

 

 

 

 

1

2

3

Total Weight (kg)

274

233

331

Total Value

$120.32

$112.96

$151.36

 

 

 

 

Silas knows that he received $0.24 per kilogram for his cabbage and $0.86 per kilogram for his broccoli. Use matrix operations to determine the weights of cabbage and broccoli he delivered each week.

Solution: Each week's delivery represents two linear equations (one for weight and one for value) with two unknown variables (the weights of cabbage and broccoli). All three weeks can be handled simultaneously using the matrix equation

⎡1

1 ⎤

d

d

d

=

⎡274

233

331 ⎤

11

12

13

112.96

0.24

0.86

d21

d22

d23

 

120.32

151.36

or

 

 

AD = B

 

 

 

 

 

where the first row of matrix D is the weights of cabbage for the three weeks and the second row is the weights of broccoli.

Keystrokes

Display

2

2.0000

v´mA

 

´>1

2.0000

´U

2.0000

1 OA

1.0000

OA

1.0000

.24 OA

0.2400

.86 OA

0.8600

2 v3

3.0000

´mB

 

Dimensions A as 2×2 matrix.

Sets row and column numbers in R0 and R1 to 1.

Activates User mode. Stores a11.

Stores a12.

Stores a21.

Stores a22.

Dimensions B as 2×3 matrix.