Calculate Total Distance: Adding 1.2, 2.1, and 1.7 Kilometers in a Three-Day Journey

To work out how many kilometres Andy walks in total, we need to add up the distances he walks each day in the following manner:

$1.2\\+2.1\\+1.7$

First we will add the digits after the decimal point accordingly:

$2+1+7=10$

Since these add up to 10, we can replace the tenths digit with a 0 and add a units digit to the number.

Now, simply add up the units digits of the number (the original digits before the decimal place plus our new one):

$1+1+2+1=5$

In total, Andy walks 5 km (5.0 km).