Question

Roberto notices that his hair is decreasing exponentially at a rate of 60% per year. If he starts with 100,000 hairs on his head, how many hairs will he have after 4 years?​

Answer 1

2560 hairs.

Explanation:

Let x be time in years and y the number of hairs.

"...exponentially at a rate of 60%", therefore:

`y=100,000(1-0.6)^(x)`

(Check image below to undestand the function).

Now, to find the amount os hairs, substitute the value of x by 4 and calculate:

`y=100,000(1-0.6)^(4)\\\\y=2560`