起初,阿里(Ali)、布兰登(Brandon)、凯莉(Carrie)和戴维(Devi)平分了一笔钱。 阿里把他钱的 23\frac{2}{3} 给了布兰登。

  1. (a)

    最后,阿里拥有的钱占这笔总金额的几分之几?

    答:(a) ___

  2. (b)

    接着,布兰登把他当时拥有的钱的 15\frac{1}{5} 给了凯莉。

    随后,凯莉把她当时拥有的钱的 38\frac{3}{8} 外加额外 $55\char36{}55 给了戴维。

    最后,戴维有了 $595\char36{}595。他们起初平分的那笔总金额是多少钱?

    答:(b) ___

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完整解法

17(a)

1. Determine Ali's initial fraction of the total sum

Since the money was shared equally among 4 people, Ali initially had 14\frac{1}{4} of the total sum.

2. Calculate the fraction of his own money Ali had left

Ali gave away 23\frac{2}{3} of his money, so he had 1−23=131 - \frac{2}{3} = \frac{1}{3} of his money left.

3. Calculate the fraction of the total sum Ali had in the end

Fraction of the total sum = 13×14=112\frac{1}{3} \times \frac{1}{4} = \frac{1}{12}

答案

112\frac{1}{12}

17(b)

1. Establish initial units for each person

Let the initial amount each person had be 33 units (to easily divide by 33).
Total sum = 1212 units.
Ali: 33 units
Brandon: 33 units
Carrie: 33 units
Devi: 33 units

2. Track Ali's transfer to Brandon

Ali gives 23\frac{2}{3} of his money to Brandon.
Ali gives 23×3=2\frac{2}{3} \times 3 = 2 units.
Brandon now has 3+2=53 + 2 = 5 units.

3. Track Brandon's transfer to Carrie

Brandon gives 15\frac{1}{5} of his money to Carrie.
Brandon gives 15×5=1\frac{1}{5} \times 5 = 1 unit.
Carrie now has 3+1=43 + 1 = 4 units.

4. Track Carrie's transfer to Devi and set up equation for Devi

Carrie gives 38\frac{3}{8} of her money and an additional $55\char36{}55 to Devi.
Carrie gives 38×4=1.5\frac{3}{8} \times 4 = 1.5 units plus $55\char36{}55.
Devi receives 1.51.5 units +$55+ \char36{}55.
Devi's final amount = Initial 33 units +1.5+ 1.5 units +$55=4.5+ \char36{}55 = 4.5 units +$55+ \char36{}55.

5. Solve for 1 unit and find the total sum

Devi had $595\char36{}595 in the end.
4.54.5 units +$55=$595+ \char36{}55 = \char36{}595
4.54.5 units =$595−$55=$540= \char36{}595 - \char36{}55 = \char36{}540
11 unit =$540÷4.5=$120= \char36{}540 \div 4.5 = \char36{}120
Total sum =12= 12 units =12×$120=$1440= 12 \times \char36{}120 = \char36{}1440

答案

$1440\char36{}1440

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