拉维先生花了他所有钱的 \frac{1}{4} 买了一件衬衫,并用剩余钱的 \frac{5}{6} 买了一个羽毛球拍、一条短裤和两双鞋。羽毛球拍的价格是一双鞋的 4 倍,而那条短裤的价格是一双鞋的 \frac{2}{3}。衬衫的价格比短裤贵 $84.30。

  1. (a)

    他花在短裤上的钱占他总资金的几分之几?

  2. (b)

    拉维先生一共花了多少钱?

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完整解法

17(a)

1. Find the fraction of the total money spent on the racket, shorts, and 2 pairs of shoes.

Fraction of money remaining after buying the shirt = 1−14=341 - \frac{1}{4} = \frac{3}{4}
Fraction of total money spent on the racket, shorts, and 2 pairs of shoes = 56×34=58\frac{5}{6} \times \frac{3}{4} = \frac{5}{8}

2. Express the cost of the items in terms of a common unit.

Let the cost of a pair of shoes be 33 units.
Cost of the badminton racket = 4×3=124 \times 3 = 12 units.
Cost of the pair of shorts = 23×3=2\frac{2}{3} \times 3 = 2 units.
Cost of 2 pairs of shoes = 2×3=62 \times 3 = 6 units.
Total cost of these items = 12+2+6=2012 + 2 + 6 = 20 units.

3. Find the fraction of the total money spent on the pair of shorts.

2020 units represents 58\frac{5}{8} of the total money.
11 unit represents 58÷20=132\frac{5}{8} \div 20 = \frac{1}{32} of the total money.
The pair of shorts costs 22 units, which represents 2×132=1162 \times \frac{1}{32} = \frac{1}{16} of the total money.

答案

116\frac{1}{16}

17(b)

1. Determine the fraction of money spent on the shirt and the remaining money

Fraction spent on shirt = 14\frac{1}{4}
Remaining fraction = 1−14=341 - \frac{1}{4} = \frac{3}{4}

2. Determine the fraction of total money spent on the group of items (racket, shorts, shoes)

Fraction spent on racket, shorts, and shoes = 56\frac{5}{6} of remaining
=56×34=58= \frac{5}{6} \times \frac{3}{4} = \frac{5}{8}

3. Express the cost of the items in terms of units of shoes

Let the cost of a pair of shoes be 11 unit (1u1u).
Cost of racket = 4u4u
Cost of shorts = 23u\frac{2}{3}u
Cost of 2 pairs of shoes = 2u2u
Total cost of these items = 4u+23u+2u=623u=203u4u + \frac{2}{3}u + 2u = 6\frac{2}{3}u = \frac{20}{3}u

4. Relate the units to the fraction of total money

The total cost of these items represents 58\frac{5}{8} of the total money.
So, 203u\frac{20}{3}u corresponds to 58\frac{5}{8} of the total money.
Therefore, 1u1u corresponds to 58÷203=58×320=332\frac{5}{8} \div \frac{20}{3} = \frac{5}{8} \times \frac{3}{20} = \frac{3}{32} of the total money.

5. Find the fraction of total money spent on the shorts

Fraction spent on shorts = 23u=23×332=116\frac{2}{3}u = \frac{2}{3} \times \frac{3}{32} = \frac{1}{16} of the total money.

6. Use the given price difference to find the total money

Fraction spent on shirt = 14=416\frac{1}{4} = \frac{4}{16}
Difference in fraction between shirt and shorts = 416−116=316\frac{4}{16} - \frac{1}{16} = \frac{3}{16}
We are given that the shirt cost $84.30\char36{}84.30 more than the shorts.
So, 316\frac{3}{16} of total money = $84.30\char36{}84.30
Total money = $84.30÷3×16=$28.10×16=$449.60\char36{}84.30 \div 3 \times 16 = \char36{}28.10 \times 16 = \char36{}449.60

7. Calculate the total amount spent altogether

Total fraction spent = Fraction for shirt + Fraction for (racket, shorts, shoes)
=14+58=28+58=78= \frac{1}{4} + \frac{5}{8} = \frac{2}{8} + \frac{5}{8} = \frac{7}{8}
Total amount spent = 78×$449.60=7×$56.20=$393.40\frac{7}{8} \times \char36{}449.60 = 7 \times \char36{}56.20 = \char36{}393.40

答案

$1011.60

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