Final answer:
Ruben and his sister hiked through the week. The total distance hiked when you add each day's distance is 2.9 kilometers.
Step-by-step explanation:
The question asks how many kilometers Ruben and his sister hiked in total during their trip. To find the total, we need to add up all the distances they hiked each day. They hiked 0.6 kilometers on Monday, 0.8 kilometers on Tuesday, 0.9 kilometers on Wednesday, 0.2 kilometers on Thursday, and 0.4 kilometers on Friday.
When we add up these distances, the sum is exactly 2.9 kilometers. Therefore, Ruben and his sister hiked 2.9 kilometers in total on their five-day trip. It's important to remember that when adding decimals, we should align the decimal points vertically to ensure correctness in the final sum.
Learn more about Adding decimals