I presume you are comparing the length of the mom's necklace to the length of her daughter's necklace. It is a 6:24 ratio, or 1:4. Also said as the mom's necklace is four times as long as the daughter's necklace. The format of the answer will depend on the grade, as they learn these various concepts (ratios/proportions versus multiples) at different ages.
I hope this helps.
DISCLAIMER: I am not a math teacher, and would welcome clarification/correction from one.