What do fractions multiply integers and fractions multiply fractions have in common
They are all the same. The denominator of an integer is 1. Because an integer divided by 1 is equal to itself, the denominator of 1 is omitted for convenience
("A / b" stands for "the fraction whose numerator is a and denominator is B")
Fraction multiplied by fraction = (numerator multiplied by numerator) / (denominator multiplied by denominator)
For example: fraction times fraction: 1 / 2 times 1 / 3 = (1 × 1) / (2 × 3) = 1 / 6
: fractional times integer: 1 / 2 times 5 = 1 / 2 times 5 / 1 = (1 × 5) / (2 × 1) = 5 / 2