Final answer:
The numbers -1.2 and -1 3/5 are rational numbers because they can be represented as fractions, -6/5 and -8/5 respectively, which fits the definition of a rational number as a quotient of two integers with a non-zero denominator.
Step-by-step explanation:
The numbers -1.2 and -1 3/5 are considered rational numbers because they can be expressed as fractions. A rational number is any number that can be represented as the quotient of two integers, where the denominator is not zero. In the case of -1.2, it can be rewritten as -6/5, which is a fraction (integer over integer). Similarly, -1 3/5 can be converted into an improper fraction as -8/5. Both these examples conform to the definition of rational numbers.
The concept of a common denominator is central to understanding how fractions can be added or subtracted. For instance, to add fractions with different denominators, you find a common denominator by multiplying the denominators together, and then adjust the numerators accordingly so you can add or subtract the fractions directly. Remember, the rules for adding, subtracting, multiplying, and dividing fractions can be built upon your natural intuition for how numbers work together.