An aquarium would vary in size depending on how big you want it, but usually the small sized aquariums are about 2.5 gallons in capacity, which converts to roughly 9.46 liters. If you were to convert this to milliliters (mL), then you multiply by 1000 to get 9460 mL. I think it's better to go with liters since the number is smaller and can be rounded to something like 9 liters.
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Soup cans vary in size/volume. One typical volume is 355 mL. Divide by 1000 to convert to liters. So 355 mL = 0.355 L. I think it's better to go with mL here because we have a whole number rather than a decimal. Also, the decimal value 0.355 isn't larger than 1, meaning we don't have a full liter.
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An eye dropper deals with a very small amount of liquid, so it's natural to go with the smaller unit mL instead of liters.
you could make a number line with 11 lines and start at .04 and go to .05 so the 11 lines will be 0.04,0.041,0.042,0.043,0.044,0.045,0.046,0.047,0.048,0.049,0.05
