Answer:
40%
Step-by-step explanation:
Remember that a percent is out of 100 parts
4/10 can be multiplied by 10 on each side to get 40/100, or 40%
Another way is to do 4/10=x/100 and cross multiply, getting 400=10x, dividing by 10 on both sides, and having x=40% (don't forget the symbol)