Why the "key word" strategy isn't always helpful

To help students through the sticky part of understanding a problem, teachers or textbooks sometimes try to provide a shortcut, often the “key word” strategy. How well does it work in the following problem?

The sum of a number and 25 is 43. What is the number?

As you know, many students will just add 25 and 43, because they see the key word of "sum" and think they're suppose to add.

We often teach students to solve these kinds of problems using the “translation” method. While this will work better for this problem than a “key word” approach, it still doesn’t help students think through the problem, so they don’t learn how to transfer what they learn in this problem to new problems.

We really want students to learn to think about situations. Thinking produces understanding. Think about a similar problem to the one above:
Tina has 25 crayons. Jim gives her some more. Now she has 43 crayons. How many crayons did she get from Jim?
Figure out two or three different ways to solve this. Did any of them involve a key word?