This is long, tedious problem . . .
Your game plan is correct!There are 5 objects that could be "on".
The probabilities for each being "on" is: .
Find the probability that 3 or more of these items are "on".
All five are on: there is one case.
Four are on: there are 5 cases.
Three are on: there are 10 cases.
Then add these 16 decimals.
I'll wait in the car . . .