Answer: Therefore, 93, 312 recipients had received the email on the 7th day
Jim needs to send email to to 128 contacts and forward email to three people.
On day 1, he sends email to 128 contacts
On day 2, each recipient send the mail to three different people
This implies that, on day 2, 1 recipient sends the email to 3 different people
Mathematically,
1 recipient = 3 people
128 recipient = x people
Cross multiply
1 * x = 128 x 3
x = 384 recipients
Therefore, on day 2, 384 recipients much have received the email
On day 3, the new recipients forwarded the email to new 3 different people
The new recipients = 384
384 x 3 = 1,152 recipients
Therefore, on day 3, 1, 152 recipients must have received the email
On day 4, 1, 152 recipients forwarded the email to another 3 different people
1,152 x 3 = 3456 recipients
Therefore, 3, 456 recipients have received the email on day 4
On day 5, 3456 recipients forwarded the email to another 3 different people
3456 x 3 = 10, 368 recipients
Therefore, 10, 368 recipients had received the email on day 5
Day 6
10, 368 x 3 = 31, 104 recipients
Day 7
31, 104 x 3 = 93, 312 recipients
Therefore, 93, 312 recipients had received the email on the 7th day