Question

BIRTHDAY BONANZA
Your eccentric Aunt Isabella sends money to eac
noney to each niece and nephew on his or her
birthday. She gives each child $10 on his or he
10 on his or her first birthday. On each birthday
thereafter, you and your cousi
nd your cousins get $20 more than on the birthday before.

How old will you be when
when you have received a total of $4,000 from Aunt Isabella?

Answer 1

Answer:

30 years

Step-by-step explanation:

In your 10 bday you get $10, then in the next (11) you get $10+$20=$30. For your 12 bday you get $30+$20=$50 and so on.

Lets try to find a formula for this, something like:

money (10) = 10

money (11) = 10 + 10 = 10 + 10(11-10)

money (12) = 10 + 20 = 10 + 10 (12-10)

.

.

.

money (t) = 10 + 10 (t-10)

Lets se how much would you have recieved when 40 years old.

total (40) = money (40) + money (39) + . . . + money (10)

You can do this sum in an excel sheet:

total (40) = 9000

So,we need less years.

If we do the same with t=30 (30 years old):

total (30) = money (30) + money (29) + . . . + money (10)

total (30) = 390 + 370 + 350 + ... + 10 = 4000

You can verify the results using a caculator or the sum function in excel.

So, when 30 years old you would have recieved $4000