Aparcel delivery service charges $2.50 to deliver packages that weigh up to 2 lb. the delivery charge for packages weighing over 2 ib, but less than 3 1/2 lb, is $2.95, for packages weighing over 3 1/2 lb, but less than 5 lb, the fee is $3.40, and so on. rosanna uses the service to send a package and is charged $4.75, what is the range of the weight of her package?

As you can see the trend is that for every 1.5 lbs it costs 0.45$ more. How did we get to know this?

Because under 2 lbs is 2.5$ and from 2 - 3.5 lbs is 2.95$ and from 3.5 - 5 lbs is 3.40$.

So if we keep following the trend we can easily calculate the range. So from 5 - 6.5 lbs it would cost 3.85$ and 6.5 - 8 it would be 4.3$ and from 8 - 9.5 lbs it would be 4.75$. Hence you have your answer.