Hi,

To explain further. Let us assume that table @t represents light bulbs being switched on and off. So the first light bulb is switched on at 9.30am and off at 10.30am, the second on at 10.00am and off at 11.00am, the third on at 10.30 am and off at 11.30am.

I need to know how long, within hour blocks, the total time expended for the sum of all light bulbs being on.

So in our example:

Between 9am to 10am, light bulb 1 was on for 0.5 hours, light bulb 2&3 were both off, so a total of half an hour (0.5)

Between 10am to 11am, light bulb 1 was on for 0.5 hours, light bulb 2 for an hour, and light bulb 3 on for 0.5 hours, so a total of 2 hours (2.0)

Between 11.00am to 12.00pm, light bulb 1 was off, light bulb 2 was off, hour, and light bulb 3 on for 0.5 hours, so a total of half an hour (0.5)