Question

Difficulty: MediumFraction Addition and Subtraction in Context

Solve the following word problem and enter your final answer as a simplified mixed number or improper fraction (e.g., 2 3/4 or 11/4).

Answer:An electrician starts a project with a spool containing 204520 \frac{4}{5} meters of copper wire. They use 6136 \frac{1}{3} meters for the kitchen circuits and 8128 \frac{1}{2} meters for the living room outlets. After these installations, there are 【5 29/30】 meters of wire remaining on the spool.

Answer

5 29/30
To find the remaining wire, the total length used must be subtracted from the original length. First, the used lengths (6136 \frac{1}{3} and 8128 \frac{1}{2}) are added by finding a common denominator of 6, totaling 145614 \frac{5}{6} meters. Next, this total is subtracted from the original 204520 \frac{4}{5} meters. A common denominator of 30 is used, converting the expression to 202430−14253020 \frac{24}{30} - 14 \frac{25}{30}. Because 2430\frac{24}{30} is smaller than 2530\frac{25}{30}, regrouping is required: 20243020 \frac{24}{30} becomes 19543019 \frac{54}{30}. Subtracting 14253014 \frac{25}{30} leaves exactly 529305 \frac{29}{30} meters.

Step-by-Step Solution

1
Find the total amount of wire used by adding the lengths used for the kitchen and living room.
613+812=14566 \frac{1}{3} + 8 \frac{1}{2} = 14 \frac{5}{6}
To determine how much wire is left, we first need to know the total amount taken from the spool. This requires finding a common denominator (6) for the fractions 13\frac{1}{3} and 12\frac{1}{2}.
2
Set up the subtraction to find the remaining wire on the spool.
2045−145620 \frac{4}{5} - 14 \frac{5}{6}
Subtracting the total used from the initial amount will give the remaining balance.
3
Find a common denominator to perform the subtraction.
The common denominator for 5 and 6 is 30. We convert the fractions: 202430−14253020 \frac{24}{30} - 14 \frac{25}{30}
Fractions must have the same denominator before they can be subtracted.
4
Borrow from the whole number to allow subtraction of the fractions.
Borrow 1 from 20 to get 19, and add 3030\frac{30}{30} to 2430\frac{24}{30}, resulting in 19543019 \frac{54}{30}. Then subtract: 195430−142530=5293019 \frac{54}{30} - 14 \frac{25}{30} = 5 \frac{29}{30}
Since 2430\frac{24}{30} is smaller than 2530\frac{25}{30}, regrouping is required to complete the subtraction.

Key Concept

Adding and subtracting mixed numbers with unlike denominators, including regrouping (borrowing).
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