Hi there, good afternoon. Mr Pang here. This question tests on concepts of changing denominator and numerator. So 2/5 = 4/10 ; 1/2 = 5/10. So the answer is somewhere 4.5/10 but it is not a fraction. We need something bigger than 4/10. One way is to make numerator bigger, another way is to make denominator smaller. So let's try making denominator smaller. = 4/9. Let us test 4/9. It is bigger than 4/10=2/5, smaller than 5/10=1/2. Bravo!