Can 12/21 and 15/24 form a proportion?

To know if two fractions are proportionate, we need to cross multiply the fractions, if their cross products are equal, then they are proportionate, if not then they are not proportionate, however we can solve for the number that will make each fraction proportionate to the other.

12/21 = 15/24

cross multiply.

12*24 = 15*21

288 = 315 * not proportionate

because we use the 1st fraction as basis, we need to adjust the 2nd fraction to make it proportionate to the 1st fraction.

12/21 we can multiply the fraction by any number as long as we multiply the number to both numerator and denominator to keep the 2nd fraction in proportion to the first fraction.