To convert 6.4 into a fraction and reduce it to its lowest terms, follow these steps:

1. Write the decimal as a fraction:
   6.4 can be written as $\frac{64}{10}$ because 6.4 is the same as 64 tenths.

2. Simplify the fraction:
   Now, simplify $\frac{64}{10}$ by dividing both the numerator and the denominator by their greatest common divisor (GCD). The GCD of 64 and 10 is 2. $\frac{64 \div 2}{10 \div 2} = \frac{32}{5}$

Thus, 6.4 as a fraction in its simplest form is $\frac{32}{5}$.

Would you like further details or have any questions?

Here are 5 related questions:

1. How do you convert other decimals like 0.75 into fractions?
2. How can you find the greatest common divisor (GCD) of two numbers?
3. How do you convert a fraction back into a decimal?
4. How would you express 6.4 as a mixed number?
5. What is the difference between proper and improper fractions?

Tip: When simplifying fractions, always look for the greatest common divisor (GCD) to make sure you're reducing to the lowest terms.