HP 15c - Manual (Page 157)

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






0.86 0.24
1 1






23 22 21
13 12
d d d
d d d
11
= 





151.36 112.96 120.32
331 233 274
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
v´mA
2.0000 Dimensions A as 2×2 matrix.
´> 1 2.0000 Sets row and column numbers in R
0
and R
1
to 1.
´U 2.0000 Activates User mode.
1 OA
1.0000 Stores a
11
.
OA 1.0000 Stores a
12
.
.24 OA
0.2400 Stores a
21
.
.86 OA
0.8600 Stores a
22
.
2 v 3
´mB
3.0000 Dimensions B as 2×3 matrix.