3/12/2010
I knew that 2nd graders study fractions this month, so I decided to give them 'fraction' problem.
The weight of the apple is 400 grams. What is the weight of 1/5, 3/10, 3/4 of that apple?
To determine the weight of 1/5, kids drew an apple and divided it into 5 parts. However it proved to be a very complicated task for them.
Then we started with more simple problem. Let's say the weight is not 400, but 100 grams. What is the weight of 1/2? Kids replied: 50 grams. Correct! What is the weight of 1/4? 25 grams, kids replied. Correct! What is the weight of 3/4? 75. Correct!
Now back to the original problem, the weight is 400 grams. What is the weight of 1/2? 200 grams. Correct! What is the weight of 1/4? 100 grams. Correct! What is the weight of 1/5? This was still difficult for kids.
I drew a circle representing an apple. Divided circle with 5 equal parts. Each part is 1/5. I marked each part with ?. We have ? + ? + ? + ? + ? = 400 grams => 5 x ? = 400 grams. What number do you need to take 5 times to get 400? Kids replied: 80. Correct! What is 2/5 then? Kids replied: 160. Correct! What is 3/5? 240. Correct!
Showing posts with label 2nd grade. Show all posts
Showing posts with label 2nd grade. Show all posts
Friday, March 12, 2010
What is the price of the book?
3/12/2010
This is another fraction problem we did today.
We know that 1/5 of the book's price is $2. What is the price of the book?
Kids solved the problem within several seconds. The answer is 10. Too easy!
This is another fraction problem we did today.
We know that 1/5 of the book's price is $2. What is the price of the book?
Kids solved the problem within several seconds. The answer is 10. Too easy!
How to get from Boston to New York?
3/12/2010
You can reach Hartford from Boston by bus and by train. You can reach New York City from Hartford by bus, train, and plane. In how many different ways you can reach New York City from Boston if you know that you shall stop in Hartford? Please note that you can change transportation in Hartford (e.g. switching from bus to train).
I asked kids to draw 3 points on the white board representing Boston, Hartford, and New York City. They connected Boston -Hartford and Hartford - New York. Then to help them visualizing they drew bus and train next to Boston - Hartford line and bus, train, and plane next to Hartford - New York line. Then they started counting all combinations: bus - bus, bus - train, etc. One girl wrote 'bus' and 'train' on the left side of her white board and 'bus', 'train', and 'plane' on the right side. Then she connected all possible combinations.
The answer is 6.
Afterward I showed to them that instead of just counting all combinations one by one they could just multiple 2 by 3, where 2 is how many different ways to get from Boston to Hartford and 3 is how many ways to get from Hartford to New York.
You can reach Hartford from Boston by bus and by train. You can reach New York City from Hartford by bus, train, and plane. In how many different ways you can reach New York City from Boston if you know that you shall stop in Hartford? Please note that you can change transportation in Hartford (e.g. switching from bus to train).
I asked kids to draw 3 points on the white board representing Boston, Hartford, and New York City. They connected Boston -Hartford and Hartford - New York. Then to help them visualizing they drew bus and train next to Boston - Hartford line and bus, train, and plane next to Hartford - New York line. Then they started counting all combinations: bus - bus, bus - train, etc. One girl wrote 'bus' and 'train' on the left side of her white board and 'bus', 'train', and 'plane' on the right side. Then she connected all possible combinations.
The answer is 6.
Afterward I showed to them that instead of just counting all combinations one by one they could just multiple 2 by 3, where 2 is how many different ways to get from Boston to Hartford and 3 is how many ways to get from Hartford to New York.
Saturday, February 20, 2010
When will we meet?
2/12/2010
I asked children to solve the following problem.
Let's say between Farmington and West Hartford is 10 miles. One person leaves Farmington and moves towards West Hartford. Another person goes from West Hartford towards Farmington. They both take the same road. The first person goes 4 miles per hour, the second 1 mile per hour. In how many hours will they meet?
I took toys and marked each mile with a toy on the floor. I asked 2 kids to volunteer . The first child stood at one end of the 'road': Farmington. The second child stood in another end: West Hartford. I asked kids where they would be in one hour. The first child stepped to the toy marking end of 4th mile. The second child moved to the toy marking end of 1st mile (from his side). Then I asked them where they would be in two hours. Kids met at 8th mile (for first child) and 2nd mile (for second child).
In how many hours will they meet? 2. Correct!
After that I changed distance and speeds calling different children and asking the same question: When will they meet?
After we were done I showed another way to solve similar problems.
I explained that in one hour both people will move 4 + 1 miles together. 4 + 1 = 5 miles. We have 10 miles total. How many times you need to take 5 miles to get to 10? 2. Correct!
I asked children to solve the following problem.
Let's say between Farmington and West Hartford is 10 miles. One person leaves Farmington and moves towards West Hartford. Another person goes from West Hartford towards Farmington. They both take the same road. The first person goes 4 miles per hour, the second 1 mile per hour. In how many hours will they meet?
I took toys and marked each mile with a toy on the floor. I asked 2 kids to volunteer . The first child stood at one end of the 'road': Farmington. The second child stood in another end: West Hartford. I asked kids where they would be in one hour. The first child stepped to the toy marking end of 4th mile. The second child moved to the toy marking end of 1st mile (from his side). Then I asked them where they would be in two hours. Kids met at 8th mile (for first child) and 2nd mile (for second child).
In how many hours will they meet? 2. Correct!
After that I changed distance and speeds calling different children and asking the same question: When will they meet?
After we were done I showed another way to solve similar problems.
I explained that in one hour both people will move 4 + 1 miles together. 4 + 1 = 5 miles. We have 10 miles total. How many times you need to take 5 miles to get to 10? 2. Correct!
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