Math Problems

This week the students are learning about liters and milliliters.  They were asked to solve the following three problems and then to explain their thinking.  Below the problems is one example of a student's response.

Haydon bought 6 water bottles.  Each water bottle contains 500 mL of water.  How many milliliters of water does Hadyon have in all?  How many liters of water does he have in all?

Miya bought 8 water bottles.  Each water bottle contains 1 liter.  She drank one half of a bottle.  How many milliliters does she have left?  How many liters does she have left?

Jaemasen has 8,500 milliliters of orange juice.  Lily has 9 liters of orange juice.  Jaemasen told Lily that he has more orange juice.  Is Jaemasen correct?  Explain.

#1:  My answer is 3 liters and I got 3,000 mL. To figure this out I first started with figuring out how many liters he had.  To figure that out I first thought well there are 6 bottles and there are 500mL. in each bottle.  So I did 6/2 which is 3.  I did that because I know that there are 1,000 milliliters in a liter and I know that 500 is half of 1,000.  So I knew that the answer is 3 liters.  Then to figure out how many milliliters there were I did 3 x 1,000.  I did that because I know that there are 1,000 milliliters in a liter. so there are 3,000 mL. because 3 x 1,000=3,000.

#2 I got 7 ½  liter and 7,500 milliliters.  To figure out this problem I thought well if there are 8 bottles of water and each bottle holds 1 liter of water I know that I should do 8x1 because each of the 8 bottles holds 1 liter of water.  After I did 8x1 which is 8 I knew that I had to subtract ½ because it said that she drank ½ of a liter. I know that 8 minus ½ is 7 ½. so she had 7 ½ liters. Then I knew that 7 x 1,000=7,000.  Then I had to do ½ of a liter more which is 500 so I did 7,000=500 which is 7,500 so I know that there are 7,500mL. and there are 7 ½ liters.

#3 My answer was no.  I know that because 8,500 mL. is equal to 8 ½ liters. Then i knew that the other person had 9 liters. To figure it out I had to compare them.  I know that he said that he had the most, but he is not correct.  I know he is not correct because 9 liters is more than 8 ½ liters. So I know that he has less orange juice than her.    

Answers and explanations were written by Brenna