Grandma currently has 250 weeds in her garden and wants to reduce the number to 30 weeds.
To find out how many weeds she needs to remove, we subtract 30 from 250:
\[ 250 - 30 = 220 \]
This means she needs to remove 220 weeds.
Given that Grandma removes weeds at a rate of 5 per minute, we can determine how long it will take her to remove 220 weeds by dividing the total number of weeds she needs to remove by her rate of removal:
\[ \frac{220 \text{ weeds}}{5 \text{ weeds/minute}} = 44 \text{ minutes} \]
Therefore, it will take her 44 minutes to have only 30 weeds remaining in the garden.