Question

Difficulty: HardSystems of Linear Equations

A logistics company packages cargo using three types of containers: small, medium, and large.

- A shipment of 33 small, 22 medium, and 11 large container has a total weight of 130130 kilograms.
- A shipment of 11 small, 44 medium, and 22 large containers has a total weight of 185185 kilograms.
- A shipment of 22 small, 11 medium, and 33 large containers has a total weight of 160160 kilograms.

What is the weight, in kilograms, of one large container?

Answer: 35 kilograms

Answer

The weight of one large container is 35 kilograms.
Representing the weights of small, medium, and large containers as variables SS, MM, and LL yields the 3x3 system of linear equations:
1) 3S+2M+L=1303S + 2M + L = 130
2) S+4M+2L=185S + 4M + 2L = 185
3) 2S+M+3L=1602S + M + 3L = 160

Solving for SS in equation (2) gives S=1854M2LS = 185 - 4M - 2L. Substituting this into equations (1) and (3) reduces the system to:
- 2M+L=852M + L = 85
- 7M+L=2107M + L = 210

Subtracting the first equation from the second yields 5M=1255M = 125, so M=25M = 25. Substituting M=25M = 25 into 2M+L=852M + L = 85 gives 50+L=8550 + L = 85, which simplifies to L=35L = 35.

Step-by-Step Solution

1
Set up a system of three linear equations based on the shipment descriptions
3S+2M+L=1303S + 2M + L = 130, S+4M+2L=185S + 4M + 2L = 185, and 2S+M+3L=1602S + M + 3L = 160
Translate the physical constraints of the three shipments into mathematical relationships
2
Isolate variable SS in the second equation and substitute into the first and third equations
Two equations in two variables: 2M+L=852M + L = 85 and 7M+L=2107M + L = 210
Reduce the 3x3 system to a 2x2 system to eliminate variable SS
3
Subtract the two simplified equations to solve for MM
5M=125    M=255M = 125 \implies M = 25
Eliminate variable LL to obtain the value of MM
4
Substitute M=25M = 25 back into 2M+L=852M + L = 85 to solve for LL
L=35L = 35
Find the requested value for the weight of one large container

Key Concept

Solving 3x3 Systems of Linear Equations using Substitution and Elimination
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