If I can buy 100 items for $9.00 or 1000 items for $22.00 what is the percentage of savings?

Question

If I can buy 100 items for a price of $9.00 and I can buy 1000 of the same item for $22.00 what is the percentage of savings?

Answer 1

If X is the unit price of an item and this is reduced by R% to unit price Y, then Y=X-XR/100, R=100(X-Y)/X.

Unit price of 100 items for $9 is 9 cents per item, so X=9.

Unit price of 1000 items for $22 is 2.2 cents per item, so Y=2.2.

R=100(9-2.2)/9=680/9=75.56%.