The total area is the product of length and width
... total area = (length1 × width) + (length2 × width)
... = (length1 + length2) × width
... 60 3/8 = (6 + 5 1/2) × width
... (60 3/8)/(11 1/2) = width = 5 1/4 . . . . feet
The width of the boards use for the set was 5 1/4 feet.
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A suitable calculator can give you this answer directly. Others may ask you to convert to or from decimal feet.
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The method conventionally taught to do division with mixed numbers is to convert them to improper fractions:
... 60 3/8 = (60·8 +3)/8 = 483/8
... 11 1/2 = (11·2 + 1)/2 = 23/2
Then, invert the denominator and multiply:
... (483/8)/(23/2) = (483/8) × (2/23) = 483/(4·23)
... = 483/92 = 5 23/92 = 5 1/4 . . . . . . . . remembering that 92 = 4·23
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It isn't clear whether this is a problem about areas, or a problem about mixed-number arithmetic. It is a good idea to get comfortable with arithmetic using numbers in any form: integers, decimals, mixed numbers, fractions, percents.
