Answer :
Consider the given number,
[tex]0.00064[/tex]As per the rule, remove the decimal from the numerator and put a 1 in the denominator. Now, the denominator of the fraction will have as many zeroes as there are number of digits in the decimal number.
Applying this rule,
[tex]0.00064=\frac{000064}{100000}[/tex]Sice the leading zeroes does not make any sense, they can be dropped,
[tex]0.00064=\frac{64}{100000}[/tex]Simplify the fraction by cancelling out by 32 (HCF of 64 and 100000),
[tex]0.00064=\frac{2}{3125}[/tex]Thus, the required fraction is 2/3125 .