To visit his grandmother, Luis takes a train 6.37 kilometers and a car 5.9 kilometers. How far is Luis’s total journey?

To find the total distance of Luis's journey, you simply add the distances he traveled by train and by car together:

\[ \text{Total distance} = \text{Distance by train} + \text{Distance by car} \]

Substituting the given values:

\[ \text{Total distance} = 6.37 \text{ km} + 5.9 \text{ km} \]

Now, let's perform the addition:

First, you can align the numbers based on their decimal points:

  6.37
+ 5.90
------

Adding them gives:

\[ 6.37 + 5.90 = 12.27 \text{ km} \]

So the total distance of Luis’s journey is 12.27 kilometers.