A new shopping mall is gaining in popularity. Every day since it opened, the number of shoppers is 20% more than the number of shoppers the day before. The total number of shoppers over the first 4 days is 671. How many shoppers were at the mall on the first day?

The number of buyers on the first day was approximately 324.

Step-by-step explanation:

In this case we have a initial number of shoppers "C" that we want to know and this grows at a steady rate of 20% per day, like a compound interest, we also know the total number of shoppers after 4 days, so we have the final amount of shoppers. We can use the formula for compound interest in order to calculate the number of shoppers in the first day as shown bellow:

M = C * (1 + i) ^ (t)

Where M is the total amount of shoppers, i is the growth rate and t is the time elapsed.

671 = C * (1 + 0.2) ^ (4)

671 = C * (1.2) ^4

671 = C*2.0736

C = 671/2.0736 = 323.5918

Since there can't be a 0.59 buyer, we will round the number to 324.