I know this subject has been covered here several times but I could not get any of the answers worked for my problem.
I have 7 packages running in a Master Package and 7th child has 3 parameters. To be able to let user define those 3 parameters, I have to ask and get them during master package run so master package needs to pass them to package number 7 that is running under it. I have the same set of 3 parameters defined in child package as well as the master but could not pass them down for some reason.
I think I found my answer and want to share it here in case somebody else needs the exact same answer: 3 parameters defined in master package level are to be mapped in execute package task editor that is used to run the 7th child package under the master. To do that, go to execute package task editor of 7th child package and go to Parameter Bindings. There, for each Child Package Parameter (those are the parameters defined in the child package) enter Binding Parameter or variable by selecting it from drop down (they are available as soon as created in master package level)