Question

Tamara texted a photo of a dolphin to 5 friends. She asked each of her 5 friends to text the photo to 5 more friends. The photo chain continued with
each person texting the photo to 5 more friends. How many photos of the dolphin will be texted after 4 rounds? Write and evaluate an expression that shows the number of photos.
B: If the photo chain continues, in which round will the photo be texted 78,125 times?
C: Tamara says her goal is to have the photo texted 1 million times. She says it will at least take until the 10th round. Is Tamara correct? Explain.

I mostly need help with Part C

Answer 1

So 5
then 5 times 5
then 5 times 5 times 5
so it seems that for x rounds, there will be 5^x 

A: 4 rounds so 5^4=625 photos
B. see how many times 5 goes into 78125. the answer is 7 so 7 rounds
C. 1 million=1,000,000 so try big numbers
5^10=9,765,625 too big
5^9=1,9,53,125 too big
5^8=390625 too small
the minimum is 5^9 or 9 rounds

A:4
B:7
C:9