Answer:
225
Step-by-step explanation:
numbers greater than 200 and less than 300 is 201-299
square numbers between such are
15^2 - 225
16^2 - 256
17^2 - 289
multiples of 5 end in 0 or 5.
225 ends in 5, whereas the other numbers do not.
the number Dave is thinking of is 225
hope this helps:)
