Always use this formula to find a percentage:
% / 100 = Part / Whole replace the given values:
4 / 100 = Part / 10
Cross multiply:
4 x 10 = 100 x Part, or
40 = 100 x Part
Now, divide by 100 and get the answer:
Part = 40 / 100 = 0.4
Use again the same percentage formula:
% / 100 = Part / Whole replace the given values:
% / 100 = 4 / 10
Cross multiply:
% x 10 = 4 x 100
Divide by 10 and get the percentage:
% = 4 x 100 / 10 = 40%