You should create an even proportion. So you could do seconds over heartbeats or the other way around. I decided to do the other way around. Since yu want to see h in m minutes and in a minute there are 60 seconds, I did 8/10 = h/60. Instead of cross multiplying, I saw that 10 times 6 is 60 so 8 x 6=h. 8 x 6 = 48 so h=48.
