Answer: the bigger bottle (90 fl. oz) is better value
Step-by-step explanation:
One method is to scale the quantities up to the same value.
The LCM (lowest common multiple) of 50 and 90 is 450
9 of the smaller bottle will cost $44.95 and contain 450 fl. oz
5 of the bigger bottle will cost $37.50 and also contain 450 fl. oz
A second method is to find the cost per (say) 10 fl. oz from each bottle
In the 50 fl. oz bottle each 10 fl. oz costs 4.99 / 5 = $0.998
In the 90 fl. oz bottle each 10 fl. oz costs 7.50 / 9 = $0.8333...
