Math Problem Statement

A person is putting oranges into a box. The dimensions of the box are 11 inches by 21 inches by 10 inches. Assuming oranges are spherical with a 2.8-inch diameter, how many oranges should fit in the box? (Hint: Packing spheres in a rectangular prism usually takes up 190% of the volume of the spheres using random packaging.)

Solution

To determine how many oranges can fit into the box, we can break down the problem step by step:

Step 1: Calculate the volume of the box

The volume VboxV_{\text{box}} of a rectangular box is given by the formula: Vbox=length×width×heightV_{\text{box}} = \text{length} \times \text{width} \times \text{height} Substituting the given dimensions of the box (11 inches, 21 inches, 10 inches): Vbox=11×21×10=2310cubic inchesV_{\text{box}} = 11 \times 21 \times 10 = 2310 \, \text{cubic inches}

Step 2: Calculate the volume of one orange

The volume VorangeV_{\text{orange}} of a sphere is given by the formula: Vorange=43πr3V_{\text{orange}} = \frac{4}{3} \pi r^3 where rr is the radius of the sphere. Since the diameter of the orange is 2.8 inches, the radius r=2.82=1.4r = \frac{2.8}{2} = 1.4 inches: Vorange=43π(1.4)343π(2.744)11.52cubic inchesV_{\text{orange}} = \frac{4}{3} \pi (1.4)^3 \approx \frac{4}{3} \pi (2.744) \approx 11.52 \, \text{cubic inches}

Step 3: Calculate the total number of oranges based on volume

If the spheres were perfectly packed, the total number of oranges NN could be estimated as: Nperfect=VboxVorange=231011.52200.52N_{\text{perfect}} = \frac{V_{\text{box}}}{V_{\text{orange}}} = \frac{2310}{11.52} \approx 200.52 So, under perfect packing conditions, around 200 oranges would fit.

Step 4: Adjust for random packing efficiency

Since random packing of spheres typically takes up around 190% of the volume of the spheres (due to inefficient use of space), we need to reduce the number of oranges accordingly: Nactual=Nperfect1.9=200.521.9105.54N_{\text{actual}} = \frac{N_{\text{perfect}}}{1.9} = \frac{200.52}{1.9} \approx 105.54

Conclusion:

Rounding to the nearest whole number, approximately 106 oranges should fit into the box.


Would you like more details on any specific part of this solution, or do you have any questions?

Here are 5 questions to explore this topic further:

  1. How does the packing efficiency affect the overall number of oranges?
  2. What would happen if the orange size changes to 3 inches in diameter?
  3. How would the result change with more efficient (hexagonal close) packing instead of random packing?
  4. What if the box had curved edges or was a cylindrical shape?
  5. How does changing the material properties of oranges (e.g., squishiness) affect packing?

Tip: Remember that efficient packing methods like face-centered cubic (FCC) or hexagonal close packing (HCP) can fit more spheres than random packing!

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Math Problem Analysis

Mathematical Concepts

Geometry
Volume Calculation
Sphere Packing Efficiency

Formulas

Volume of a rectangular box: V_box = length * width * height
Volume of a sphere: V_sphere = (4/3) * π * r^3
Packing efficiency adjustment: N_actual = N_perfect / packing efficiency

Theorems

Sphere packing efficiency theorem

Suitable Grade Level

Grades 10-12