Answer:
Step-by-step explanation:
The savings for each month is increasing by 20%. It means that it is increasing in geometric progression. The formula for determining the sum of n terms, Sn of a geometric sequence is expressed as
Sn = (ar^n - 1)/(r - 1)
Where
n represents the number of terms(months) in the sequence.
a represents the first term in the sequence.
r represents the common ratio.
From the information given,
a = $125
r = 1 + 20/100 = 1.2
From March to August, it is 5 months. Thus,
n = 5 months
Therefore, the sum of the first 8
5 terms(months), S5 is
S5 = (125 × 1.2^(5) - 1)/1.2 - 1
S5 = (125 × 1.48832)/0.2
S5 = 186.04/0.2
S5 = $930.2
They won't have enough money for the trip.
The additional amount of money that they need is
1370 - 930.2 = $439.8
