Question

A teacher asked her students to design a cold pack. The desired criteria and constraints for the cold pack are as follows:
it should be as cold as possible
it should stay cold for about 5 minutes
it should be reusable
The students were instructed to mix ammonium nitrate crystals in plastic bags filled with water. They were split into three groups, and each group created a design. Each design used a different amount of ammonium nitrate crystals. The table shows the cold pack designs created by the three groups.

Temperature Maintained (°C) Amount of Time it Stays Cold (minutes) Reusability
Design 1 4-6 5 twice
Design 2 3-5 3 twice
Design 3 5-7 7 once

How could the designs be combined to best meet the criteria and constraints?
A.
temperature maintained by Design 1 and time Design 3 stays cold
B.
reusability of Design 3 and time Design 2 stays cold
C.
reusability of Design 2 and temperature maintained by Design 3
D.
temperature maintained by Design 2 and time Design 1 stays cold

Answer 1

To determine which combination of designs best meets the criteria and constraints, we need to focus on the three key requirements: the coldness of the temperature maintained, the duration it stays cold, and the reusability.

1. **Temperature Desired**: As cold as possible.
2. **Time Requirement**: Should stay cold for about 5 minutes.
3. **Reusability**: Should be reusable.

Analyzing the designs:

- **Design 1**: Maintains a temperature of 4-6°C and stays cold for 5 minutes, reusable twice.
- **Design 2**: Maintains a temperature of 3-5°C and stays cold for 3 minutes, reusable twice.
- **Design 3**: Maintains a temperature of 5-7°C and stays cold for 7 minutes, reusable once.

Now, let's evaluate the options provided:

A. **Temperature maintained by Design 1 and time Design 3 stays cold**:
- Temperature: 4-6°C (Design 1)
- Time: 7 minutes (Design 3)
- Reusability: Not mentioned (Design 3 is once)

B. **Reusability of Design 3 and time Design 2 stays cold**:
- Reusability: Once (Design 3)
- Time: 3 minutes (Design 2)
- Temperature: Not mentioned (but would be 3-5°C, which is lower)

C. **Reusability of Design 2 and temperature maintained by Design 3**:
- Reusability: Twice (Design 2)
- Temperature: 5-7°C (Design 3)
- Time: Not mentioned

D. **Temperature maintained by Design 2 and time Design 1 stays cold**:
- Temperature: 3-5°C (Design 2)
- Time: 5 minutes (Design 1)
- Reusability: Not mentioned

Considering the requirement of maintaining the lowest temperature possible while meeting the time constraint of staying cold for about 5 minutes, **Option A** seems the most appealing, as it offers the best combination of temperature (4-6°C from Design 1) and a longer time (7 minutes from Design 3), although it sacrifices reusability.

Thus, **the best combined approach** to meet the criteria and constraints would be:

**A. temperature maintained by Design 1 and time Design 3 stays cold**.

This combination prioritizes maintaining a colder temperature and maximizes the time the pack remains cold, even though it does not consider reusability.