The key word in this problem is

*.*

**nearest ten**The nearest ten below 50 starts at 45. Why? Because the last digit is 5. At 5, we round up to the nearest ten.

Therefore, the least number of marbles in the bag is 45 since it rounds up to 50 for the nearest ten

The greatest number above 50 rounded to the nearest ten is 54, because less than 5 on the last digit means we round down.

Therefore, the greatest number of marbles in the bag is 54 since it rounds down to 50 when the last digit is less than 5

Answer:

{

**45, 54}**