Davis notices that his hair is decreasingly exponentially at a rate of 10% per year. If he starts with 100,000 on his head, how many will he have after 3 years?

If we start with the first year we have 0 hair loss or 100000 hairs remaining.

After the first year we have a 10% hair loss so we've lost 10000 hairs remaining.

Second year we have a 20% additional hair loss so we've got 9000 hairs remaining.

Third year we have 30% additional hair loss so we've got 6300 hairs left.