Question

A woman deposits 100 EUR in her daughter's bank account on her first birthday. On every subsequent birthday, she deposits 10 EUR more than she deposited the previous year, so on her second birthday, she deposits 110 EUR, and on her third birthday she deposits 120 EUR. By the time her daughter is 21 years old, how much money has been deposited in her account?

Answer 1

We will solve this using APs.

a = 100, d = 10, n = 21

So,

a₂₁ = a + (n-1)d

a₂₁ = 100 + (21-1)10

a₂₁ = 100 + (20)10

a₂₁ = 100 + 200

a₂₁ = 300

Now, we can solve for S₂₁

S₂₁ = S/2(a + a₂₁)

S₂₁ = 21/2(100+300)

S₂₁ = 21/2(400)

S₂₁ = 21*200

S₂₁ = 4200

Hope this Helped!

Stay safe, stay sanitized and stay blessed!

ヾ(•ω•`)oヾ(•ω•`)o