What is the relationship between time, scope, and cost of a project?

Question

I know about the project management triangle, and that the time, the scope, and the cost of any projects represent an edge in that triangle, this is just too technical for me. In real life, what is the relationship between the 3 of them?

Answer 1

Here's how they relate to each other:

To get all the deliverables (in the project scope) done, you will need resources to spend time working on the deliverables, you may also need some material.

In other words:

Scope = Time + Expenses (material, rent, etc...)

But resources' time costs money (these costs can be either direct or indirect costs, see: http://www.projectmanagementquestions.com/1509/what-are-two-examples-of-a-direct-cost-and-indirect-cost )

So now we have that...

Scope = Salaries + Expenses

But both salaries and the expenses are considered to be costs (direct or indirect)

So we have that...

Scope = Cost

Of course, I have applied a philosophical approach to the project triangle, I hope you enjoyed it!

Here are some things that you need to know:

Time increase means there is definitely a cost increase, but not necessarily a scope increase.
Cost increase is not necessarily equal to time decrease or scope increase.
Scope increase means cost increase and time increase.
Scope decrease does not necessarily mean cost decrease or time decrease.
Cost decrease means scope decrease and (usually) time decrease.
Time decrease does not mean there is a cost decrease, but may mean there' a scope decrease.

Answer 2

what is the relationship between time and costs?