Math Problem Statement

The construction crew for a new house will dig a hole in the shape of a rectangular prism for the house's foundation. The hole will be 54 ft long, 45 ft wide, and 12 ft deep. To haul away all of the dirt from the hole, a dump truck will take trips to a nearby landfill. The crew knows the amount of dirt the truck can hold each trip in cubic yards.

Solution

Let's break down the problem step by step based on the image provided.

(a) Find the volume of dirt that will be hauled away in cubic yards.

The hole is in the shape of a rectangular prism, and the dimensions are:

  • Length: 54 feet
  • Width: 45 feet
  • Depth: 12 feet

The volume VV of a rectangular prism is calculated by the formula: V=length×width×heightV = \text{length} \times \text{width} \times \text{height} This will give us the volume in cubic feet. However, we need to convert this to cubic yards.

1 yard = 3 feet, so: 1 cubic yard=(3feet)3=27cubic feet1 \text{ cubic yard} = (3 \, \text{feet})^3 = 27 \, \text{cubic feet}

Now, calculate the volume in cubic feet: V=54×45×12=29,160cubic feetV = 54 \times 45 \times 12 = 29,160 \, \text{cubic feet}

Convert cubic feet to cubic yards: Volume in cubic yards=29,16027=1,080cubic yards\text{Volume in cubic yards} = \frac{29,160}{27} = 1,080 \, \text{cubic yards}

So, the volume of dirt is 1,080 cubic yards.

(b) How many trips are needed to haul all of the dirt away?

Each trip, the truck can haul 17 cubic yards. To find the number of trips needed: Number of trips=Total volume of dirtVolume per trip=1,0801763.53\text{Number of trips} = \frac{\text{Total volume of dirt}}{\text{Volume per trip}} = \frac{1,080}{17} \approx 63.53 Since the crew cannot make a fraction of a trip, we round up to 64 trips.

So, 64 trips are needed.

(c) Total cost to haul away the dirt?

The cost per trip is $1,125. To find the total cost, multiply the number of trips by the cost per trip: Total cost=64×1,125=72,000dollars\text{Total cost} = 64 \times 1,125 = 72,000 \, \text{dollars}

So, the total cost is $72,000.


Would you like further details on any part of this solution? Here are some related questions to explore:

  1. How would the volume change if the depth of the hole increased by 3 feet?
  2. What would the cost be if the truck could carry 20 cubic yards per trip instead of 17?
  3. If the cost per trip increased by 10%, how much more would it cost in total?
  4. How many trips would be needed if the hole dimensions were doubled?
  5. What is the impact of rounding up trips on the total cost?

Tip: Always ensure to convert units correctly when dealing with different measurement systems to avoid calculation errors.

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Math Problem Analysis

Mathematical Concepts

Volume of a Rectangular Prism
Unit Conversion
Division
Rounding

Formulas

Volume = length × width × depth
1 cubic yard = 27 cubic feet
Trips = Total volume / Volume per trip

Theorems

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Suitable Grade Level

Grades 6-8