Evaluate: b. `4 div (16)/(21)`

Answer

To evaluate the expression \( 4 \div \left(\frac{16}{21}\right) \), we can follow these steps:

### Step 1: Rewrite the Division as Multiplication
The expression \( 4 \div \left(\frac{16}{21}\right) \) can be rewritten using multiplication by taking the reciprocal of the fraction. This gives us:
\[ 4 \div \left(\frac{16}{21}\right) = 4 \times \left(\frac{21}{16}\right) \]

### Step 2: Convert 4 to a Fraction
We can express the whole number 4 as a fraction:
\[ 4 = \frac{4}{1} \]
So now we have:
\[ \frac{4}{1} \times \frac{21}{16} \]

### Step 3: Multiply the Fractions
Now, we multiply the numerators and the denominators:
\[ \frac{4 \times 21}{1 \times 16} = \frac{84}{16} \]

### Step 4: Simplify the Fraction
Next, we simplify \( \frac{84}{16} \) by finding the greatest common divisor (GCD) of 84 and 16, which is 4:
\[ \frac{84 \div 4}{16 \div 4} = \frac{21}{4} \]

### Final Answer
Thus, the final answer is:
\[ \frac{21}{4} \]

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