if 24 hours is 100%, then 1% is 24:100, which is 0.24 of an hour. to find out how many % your first activity(10h) is, you need to find how many times one %(0.24) goes into 10h, so 10:0.24.
10:0.24=41.66... or 41.67%
45 min is 0.75h
0.75:0.24=3.125%
make sure that the total of hours is 24 and the total of % is 100.