Final Answer:
The numbers that can be written as fractions and are therefore rational are 8√8 and 10√10.
Step-by-step explanation:
Rational numbers are those that can be expressed as a fraction of two integers. In the given options, 8√8 and 10√10 can be rationalized to rational numbers.
Starting with 8√8, let's simplify it. 8√8 = 8 * (8^0.5) = 8 * 2 = 16. Since 16 can be expressed as the fraction 16/1, it is a rational number.
Now, consider 10√10. Similarly, 10√10 = 10 * (10^0.5) = 10 * 3.162 = 31.62. Again, this can be expressed as the fraction 3162/100, simplifying to 1581/50. Thus, 10√10 is a rational number.
Moving on to the decimal representations, 0.12345678910... is a rational number. Although it has an infinite decimal expansion, it follows a repeating pattern (0.123456789101112...), making it a rational number.
Lastly, 0.89898989... is also rational. It is a repeating decimal with the pattern 89, making it representable as the fraction 89/99.
In conclusion, all the provided numbers can be expressed as fractions, and therefore, they are rational numbers.