Respuesta :
Answer:
Around 0.40
Step-by-step explanation
If she doubles the gift every year, do 18x2=36, 36 rounds to 40 or 0.40.
The total of all the gifts on the girl's 18th birthday given from her grandma for this considered case is evaluated as 2621.43 dollars
What is the sum of the terms of a geometric series till nth term?
Lets suppose the geometric sequence has its initial term is [tex]a[/tex], multiplication factor is r, then, its sum is given as:
[tex]S_n = \dfrac{a(r^n-1)}{r-1}[/tex]
(sum till nth term)
The sequence would look like [tex]a, ar, \cdots, ar^{n-1},\cdots[/tex]
For this case, we are specified that:
- Grandma gives 1 penny on first birthday of her granddaughter
- Grandma increases the gift by doubling the previous birthday gift.
That shows that the gift amounts each year will form a geometric sequence where a = 1, and r = 2 (as amounts are doubled).
The gift amounts would look like:
[tex]\\1, 2, 4, \cdots\\or\\1, 2\times 1, 2^2 \times 1, \cdots[/tex]
We have to find these terms' sum till 18th term(18th term is the gift of her 18th birthday).
Thus, we have: n = 18, a = 1, and r = 2.
The sum will be:
[tex]S_n = \dfrac{a(r^n-1)}{r-1} = \dfrac{1(2^{18}-1)}{2-1} = 2^{18} - 1 = 262143 \: \rm cents[/tex]
There are 100 cents in 1 dollars,
Thus, 1 cent = 0.01 dollars,
and thus, 262143 cents form 2621.43 dollars.
Thus, the total of all the gifts on the girl's 18th birthday given from her grandma for this considered case is evaluated as 2621.43 dollars
Learn more about sum of terms of geometric sequence here:
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