Question

Your eccentric Aunt Isabella sends money to each niece and nephew on his or

Answer 1

Answer:

20 years old

Step-by-step explanation:

Given

Base Amount = $10

Additional Amount = $20

Required

Determine the number of years where the total will accumulate to $4000

This question represents Sum of an AP series.

$S_n = \frac{n}{2}(2a + (n - 1)d)$

Such that:

$S_n = 4000$

$a = 10$

$d = 20$

Substitute these values in the above formula:

$4000 = \frac{n}{2}(2 * 10 + (n - 1) * 20)$

$4000 = \frac{n}{2}(20 + 20n - 20)$

$4000 = \frac{n}{2}(20n)$

$4000 = \frac{20n^2}{2}$

$4000 = 10n^2$

Divide through by 10

$400 = n^2$

Take square root of both sides

$20 = n$

$n = 20$