Answer:
7.31 times.
Step-by-step explanation:
We have been given that Grand Canyon is approximately 29 kilometers long. Mariner Valley is a canyon on Mars that is approximately 212 kilometers long.
To find the number of times Mariner Valley is longer than the Grand Canyon, we will divide 212 by 29.
[tex]\frac{212}{29}=7.3103448\approx 7.31[/tex]
Therefore, the Mariner Valley is 7.31 times longer than the Grand Canyon.