English World 4: Unit 11 Grammar p.112 Explanation

(Supplementary Materials for Specific Textbooks--English World 4)

[A colleague of mine was confused by this page in the textbook, and I wrote him an email to try and explain it.  I figured I would add this to my list of English World 4 material.]

I was thinking, and I thought maybe I didn't explain the present perfect as well as I could have.  So here is some more information.

Both the present perfect and the past simple both refer to events in the past.  But the present perfect is unique in that it is looking at the past from the point of view of how it impacts the present.

There are several different uses of the present perfect, but the use on page 112 is "past action with a present result"

So looking at page 112, the example sentences from the book are all trying to illustrate this.
"I have painted the table" (the action is in the past, but the result is the newly painted table that you can now see before you)
"I have made a cake" (the action is in the past, but the result is the freshly baked cake that I am currently holding).
Unfortunately, as is typical with English World, not all of their example sentences are well chosen.  For example 2C (they have climbed the mountain) isn't really great at illustrating the present result.  (I guess the present result is that they are at the top of the mountain now, after having spent the day climbing it).

But the general idea they are trying to emphasize is past action with present result.

FYI:
The textbooks often have a tendency to present the contrast between verb tenses as a lot stricter than they are in real life.
In real life, a native speaker might use the past simple for any of the situations on page 112.
Also in real life, the difference between the past simple and the present perfect is based more on how the speaker feels about the event, and less about the actual context.  In all of the situations on page 112, the past simple would be fine as well, but if the speaker feels they want to emphasize the present result, they would chose the present perfect over the past simple

But that's just FYI.  I wouldn't try to explain that to the kids.  For simplicity's sake, just follow the lead of the textbook, and teach them that the present perfect is used whenever there is a present result of a past action.