How many more can I add I'm making a video with lots of pictures. The video has 85 pictures that go on for 5 seconds each I made a narratation with it aswell that goes up to 11 minutes and 31 seconds so how many more photos can I add that can make the video go up to 11 minutes and 31 seconds.
 A: Knowing that there are $60$ seconds in every minute, compute the number of seconds $S$ in $11$ minutes and 31 seconds (compute $S = 11 \times 60 + 31 = 691 = 690 + 1)$. Divide $S$ by $5$. That will give you $N = 138.2$  the number of pictures you need over the course of the entire narration. Since you have $85$ pictures already, subtract $85$ from $N = 138.2$, and that will give you the number of photos ($138.2 - 85 = 53.2$ photos) you need to add. 
Note that $53$ more photos, in addition to your current $85$ will fill $138 \cdot 5 = 690$ seconds. You need to decide whether to flash an extra photo for one second only to cover the $691$st second, or to "flash", say, the last of the 138 photos for $6$ seconds, instead of $5$ seconds, to fill that extra second (or whether to chop off 1 second from the narrative to make it an even 11 minutes and 30 seconds = $690$ seconds.)
A: $11 \text{ min } 31 \text{ sec}$ is $691\text{ sec}$. Every photo requires $5\text{ sec}$, so you can fit $\dfrac{691}5=138.2$ photos. $138$ photos will occupy $138*5= 690$ seconds. So you might have to do something about the last second.
