1. Find the 10 % of it first
(Move decimal one place to the left)
Ex. 10 percent of 78 is 7.8, 64 is 6.4, 345 is 34.5, 1.352726 is 0.1352726 etc.
Then multiply the 10% by the 1st didgit of the given percent.
Ex. 80% of 65.4
6.54
X 8= 52.32!
Hope this helped!