What kind of assignment takes you the longest?

For my level 3 childcare course we get a range of different assignments to complete for each unit and I'm finding that different types take me different times even when they are for the same grade.

For example, I am working through the sheet (it goes from D-A* and we have to complete them all, hand them in and then we get told which grades we passed. If we don't any of the grades we get one more submission and then that's the grade we get for the unit) and I'm doing my D grade stuff so they should all be around the same difficulty level which is why I don't get why some take so much longer than others.

The first thing we had to do was a leaflet (it took me a few weeks but if I had sat down and just done it it would have probably taken me around 4-6 hours as it was 2 criterias in one) and then I did this big timeline with loads of things on development which took me about 4-5 hours and I started and finished that in the same day. I'm starting an essay now but it took me about twenty minutes just to figure out what to write in a short introduction and right now I have no idea how to continue it... We don't get word counts so I just have to decide how much will be enough depending on the grade criteria as well...

Does it take you longer to do and start different types of assignments? I like writing stories so I didn't think it would be any harder for me to write an essay than it was to do other parts of my work... D: