Where Does the Decimal Go?

Multiplication

1. (using calcular) to calculate 24x63

2. Then calculate: 0.24 × 6.3; 24 × 0. 63 2.4 × 63; 0. 24 × 0.63;

3. compare the answer and see what you pattern you find.

4. pick up another two numbers by your self and then multiply them to get the answer.

5. Then put a decimal point at any place then calculate the result.

Activity 14.16

Where Does the Decimal Go?

Division

CCSS-M: 5.NBT.B.7; 6.NS.B.3

1. (using calcular) to calculate 146 ÷ 7 =

2. Then calculate: 146 ÷ 0. 7; 1. 46 ÷ 7; 14. 6 ÷ 0. 7; 1460 ÷ 70

3. compare the answer and see what you pattern you find.

4. Compare the result you get from the previous activity how does they different? And Why?

compare and draw the model:

0.38___ 0.4

0.12___0.09

2.3___2.03

Reflection: How you use model decide which one is greater

Questions: What does "attend to precision"?

Can math equations have two answers?

Why do we need to estimate or just get the estimated answer?

Mathematical ideas abound in this story about Milo’s adventures in Digitopolis, where everything is number-oriented.

There he meets a half of a boy, appearing in the illustration as a boy cut from top to bottom. But, the boy is actually 0.58

because he is a member of the average family: mother, father, and 2.58 children. One advantage, he explains, is that he is the only one who can drive 0.3 of a car, as the average family owns 1.3 cars. An extension is to explore averages that are interesting to students (average number of siblings, etc.) and see where these odd decimals come from. Illustrating an average number of pets can be very humorous!

Questions: Why context important? Generally what things can be used with decimals/fraction? what cannot? Explain and give examples.

using for finding the equal value (decimal/fraction/ratio/percentage)

Q: Do you thinking it is proper for grade 3-5 why or why not? How about higher grade? If does not fit, what the calculator needs more?

Does the fraction Model an effective tools why or why not?

1. How long is the big paperclip? Estimate

2. Write an estimate you know is too high.  Write an estimate you know is too low.

3. After every one find give the estimation. Find out the average of the all people answer (can use calculation).

   Act 3:

4. After comparing the average and other answer with the final answer.

   Which is closer?

When students are encouraged to make things, they measure things precisely, where the decimal number often appears to show the work of the students. The more precise a design, the more safe and successful will be. Through the decimal students are required to see how precision is important, even if they many times feel lazy about putting more effort into it.

God protects us from various dangers, but we are all responsible for our lives as well. Designing things with more accuracy is also related to the safety we need. In real life, students can see various examples that lack of precision can be dangerous to our lives when we are using tools or objects that are created by humankind.