Question

Kris forwards an e-mail to 5 people. Each of those people forward that e-mail to 5 more people. If this happens 2 more times, which expression shows the total number of people who have recived the e-mail, not including Kris

Answer 1

Answer:     $5+5^2+5^3+5^4$

Explanation:

1) First forwarding: 5 e-mails

2) Second forwarding: 5 * 5 =    $5^{2}$

3) Third forwarding: 5 * 5 * 5 =     $5^{3}$

4) Fourth forwarding: 5 * 5 * 5 * 5 =     $5^{4}$

The number of people who have received the email, after Kris started forwarding the e-mail, not counting Kris, is:

$5+5^2+5^3+5^4$