What is the new amount when you increase 40 by 25%?

In order to do this, you would multiply 40 by 1.25, which would be 50. Another way to do it, (this way uses more work, but you can use it to double check your answer) would be multiplying 40 * 0.25 (which equals 10) then add the answer onto the number. 40 + 10 = 50.