Answer :
Answer: [tex]a_1=50,d=25[/tex] and $475 deposited into the account on her birthdays by her 18th birthday.
Step-by-step explanation:
It is given that, on Gabriela’s first birthday, her parents gave her a $50 savings account.
Initial term : [tex]a_1=50[/tex]
On every birthday after that her parents added to the account, increasing the amount they deposited by $25 each year.
Common difference : [tex]d=25[/tex]
It forms an AP: 50,75,100,...
nth term of an AP is
[tex]a_n=a_1+(n-1)d[/tex]
Substitute [tex]a_1=50[/tex] and [tex]d=25[/tex] in the above formula.
[tex]a_n=50+(n-1)25[/tex]
It represents the amount deposited into the account after n birthdays.
We need to find the amount by her 18th birthday.
Put n=18 in the above equation.
[tex]a_{18}=50+(18-1)25[/tex]
[tex]a_{18}=50+(17)25[/tex]
[tex]a_{18}=50+425[/tex]
[tex]a_{18}=475[/tex]
Therefore, $475 deposited into the account on her birthdays by her 18th birthday.
We are to calculate total amount given to Gabriela on her 18th birthday
Total amount Gabriela’s parents will have deposited into the account on her birthdays by her 18th birthday is $475
Amount given to her on her first birthday = $50
Additional amount given to her each year = $25
number of years, n = 18
a1 = $50
d = $25
n = 18
Sum = a1 + (n - 1)d
= 50 + (18 - 1)25
= 50 + (17)25
= 50 + 425
= 475
sum = $475
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