+23 to solve the question, you need to find all the multiples of 16 and 25, and then subtract the overlap.
4000/16 = 250, so there are 250 multiples of 16 that work.
4000/25 = 160, so there are 160 multiples of 25 that work.
The overlap in this question occurs when a number is divisble by both 16 and 25. We counted those overlapping numbers twice so we need to go back and subract them off once.
4000/(16*25) = 4000/400 = 10, so there are 10 overlapping numbers.
The final answer to this problem, therefore, is 250 + 160 - 10 = 400
Hope this solutions helps!
