Which is larger, 0.4 or 0.45?

In the American decimal system, 0.45 is larger than 0.4. When comparing decimals, start from the left and compare each place value. In this case, both numbers have the same digit in the tenth place, but 0.45 has a larger hundredth place digit than 0.4. Therefore, 0.45 is greater than 0.4. It's important for 6th graders to understand the concept of place value when comparing decimals to build a strong foundation in math.