Answer:
First term = a = 125
Step-by-step explanation:
Question: find the number of shoppers on the first day
This is a geometric progression question
The sum of the terms = 671
Sum of a geometric sequence,Sn = (ar^n - 1) / (r - 1)
Where,
n = number of term in the sequence.
a = first term in the sequence.
r = common ratio
r = 1 + 20%
= 1 + 20/100
= 1 + 0.2
= 1.2
n = 4 (first 4 days)
Sn = (ar^n - 1) / (r - 1)
Sn = 671 where n = 4
671 = {a × 1.2^(4) - 1} / 1.2 - 1
671 = {a × 2.0736 - 1} / 0.2
671 = (2.0736a - a) / 0.2
671 = 1.0736a / 0.2
671 = 5.368a
Divide both sides by 5.368
a = 671 / 5.368
a = 125
