The answer is 20%.
We know, that 2 feet is 100%
100%=2 feet
10%=0.2 feet
Now, what was the drop? 2-1.6 is 0.4 feet. Now, let´s divide the drop by 10%.
0.4/0.2=2
2 times 10% is 20%. That is the answer.
I hope I helped you. I will be happy, If you mark my answer as the brainliest.