The jars of peanut butter that I buy cost $7.20 each and normally contain 500 grams. At present, however, each jar contains an extra 20% free, and, additionally, the supermarket has a "buy 3 jars get another one free" offer in place this week. By how much is the cost per 100 grams of peanut butter less than it normally is if I take full advantage of the supermarket's offer today?

$0.54

Step-by-step explanation:

Given:

The jars of peanut butter that I buy cost $7.20 each and normally contain 500 grams.

At present, however, each jar contains an extra 20% free.

And additionally, the supermarket has a "buy 3 jars get another one free''.

Question asked:

By how much is the cost per 100 grams of peanut butter less than it normally is if I take full advantage of the supermarket's offer today?

Solution:

Cost of a jars of peanut = $7.20

Normally, weight of peanut butter in one packet = 500 gram

At supermarket offer, each jar contains an extra 20% free, means a packet  of peanut butter contains = 500 + 20% of 500                                                                                                            

And extra benefit = buy 3 jars get another one free, means we will get 4 jars by just giving price of only 3 jars.

That means, total weight of peanut butter you are getting by giving 3 packet's price =  Each jar weigh number of jars

                       = 600 4 = 2400 gram

Cost of each packet will be same as previously as during the offer; $7.20

Cost of 3 packet's peanut (2400 gram) =  

Now, we will calculate cost per 100 grams of peanut butter :

During offer:

Cost of 2400 grams of peanut butter = $21.6

Cost of 1 gram of peanut butter =

Cost of 100 gram of peanut butter =

Normal day:

Cost of 500 grams of peanut butter = $7.20

Cost of 1 gram of peanut butter =

Cost of 100 gram of peanut butter =

We found that cost of 100 gram of peanut butter in normal day is $1.44 while cost of 100 gram of peanut butter during offer is $0.9 means cost per 100 gram during offer is ($1.44 - $0.9 = )$0.54 less than cost during normal day.

Conclusion:

Therefore, cost per 100 grams of peanut butter is $0.54 less than it is normally if you take full advantage of the supermarket's offer today.