The number between 0.754646 and 0.755646 must be greater than 0.754646 and smaller than 0.755646. In 0.756446, 0.756464 and 0.756647, digits till hundredth place are same but digit at ten thousandth place is greater than that of 0.755646. So, they are greater than 0.755646. So, only 0.755464 can be the answer.