Lori needs at least 12 liters of water to fill a water cooler. She has a container with 4.55 liters of

water, a container with 3.25 liters of water, and a container with 4.85 liters of water. Does she

have enough water? Use estimation only to decide. Explain why you are confident in your

estimate.

Yes, she has enough water.

Explanation:

To estimate the value, you can work with friendly numbers: numbers closed to the given numbers and with which you can perform easy mental calculations.

For example 4.55 may be rouned to 5, 4.85 may be rounded to 5, and 3.25 may be rounded to 3. That yields 5 + 5 + 3 = 13

Then, it seems you have about 13 liters. Is the final number equal or greater than 12 for sure?

To round 4.55 to 5 you increased the amount in 0.45, to round 4.85 to 5 you increased the amount by 0.15, and to round 3.25 to 3 you decreased the amount in 0.25.

What was the net change in your values: 0.45 + 0.15 - 0.25 = 0.60 - 0.25 = 0.35. Those are easy calculations that you can perform in your mind.

That means that you increased your total in less than 1 liter. Meaning that the final total is overestimated by 0.35, and that if you used the real amounts to make the calculations, the total will be still more than 12.