13 凯瑟琳订购了一篮水果，里面仅包含苹果、橙子和梨。 其中 $\frac{5}{16}$ 的水果是苹果。剩余水果的 80% 是橙子。 另外的 11 个水果是梨。 求篮子中苹果的数量。 答案 ___ 个苹果

1. Find the fraction of fruits remaining after the apples are removed.

Fraction of fruits that are not apples:

$1-\frac{5}{16}=\frac{11}{16}$

2. Find the fraction of the total basket that are pears.

Since $80\%$ of the remaining fruits are oranges, the pears are $20\%$ of the remaining fruits.

$20\%\times \frac{11}{16}=\frac{20}{100}\times \frac{11}{16}=\frac{1}{5}\times \frac{11}{16}=\frac{11}{80}$

So pears are $\frac{11}{80}$ of all the fruits.

3. Use the number of pears to find the total number of fruits, then find the number of apples.

The $11$ pears represent $\frac{11}{80}$ of the total number of fruits.

Let the total number of fruits be $T$.

$\frac{11}{80}T=11$

$T=11\div \frac{11}{80}=80$

Number of apples:

$\frac{5}{16}\times 80=25$