This is not 4 different problems.
It's the same problem 4 times.
The Rule: To find the unit rate, divide the price by the quantity.
Just like you wrote in pencil next to #6 and #8 .
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#6). Look at The Rule up above.
Unit price for Brand A: $4.80 / 32 oz = 15¢ per oz.
Unit price for Brand B: $5.76 / 48 oz = 12¢ per oz.
Unit price for Brand C: $17.92 / 128 oz = 14¢ per oz.
#7).
IF the price is the ONLY thing that's different about them, then Brand-B
is the best choice, because it's the lowest price per ounce.
BUT ... there may be other things to compare:
Do they all get your dishes equally clean ?
Do they all rinse off equally easily ?
Do they all smell the same ?
Do any of them attract bugs when they stand around ?
Do any of them spoil when they stand around open ?
You may want to consider other things besides the price
when you're deciding which detergent to buy.
#8). Look at The Rule up above again.
Unit rate for Regular size = $3.36 / 16 oz = 21¢ per oz.
Unit rate for Family size = $7.60 / 40 oz = 19¢ per oz.
#9).
Again ... IF the cost is the ONLY thing to think about, then the Family size
is the better buy, because it costs 2¢ less for every ounce.
But there may be other things to consider. Does the peanut butter from
both sizes taste the same ? Does one taste better ? Is the Family size
so big that it might be hard to handle, and you may drop it by accident ?