announcements last day to drop without a w is 12 february first exam: 13 february class notes in the...
Post on 20-Dec-2015
214 views
TRANSCRIPT
Announcements• Last day to drop without a W is
12 February
• First exam: 13 February
• Class Notes in the Bookstore. Need by 19 February. Cost is $3.50.
What is wrong with saying 372 What is wrong with saying 372 base 6base 6? ?
What is a proper way of writing this What is a proper way of writing this number in base 6?number in base 6?
Let’s add in Alphabitia BCD
+ DB
BCD is DB is BCD + DB is
You try:
B0B+ABC
Use the manipulatives or draw pictures to help explain your answer.
Let’s subtract
CBD- ADC =
CBD is ADC is CBD - ADC is
You Try…
D00-B0B
B0A-BD
You try: Use manipulatives or drawings to explain
BBC - A0C
A0A0D - BCA
Exploration 3.1
• In your groups: Do Part 1, #1 and #2a
• Then do Part 2, #1 and 2
Begin Addition• Ways to represent addition:• 1. Counters
• 2. Number Line
• 3. Part-Part Whole a b
c
0 2 4 6 8 10
Vocabulary• A + B = C• A and B are called Addends• C is called the Sum• Since A + B = B + A every time, we give it a
special name: commutative property.• Since A + (B + C) = (A + B) + C every time,
we give it a special name: associative property.
Addition and Place Value• If we have 154 + 69
Mental Arithmetic
• 39 + 57
Mental Arithmetic• 39 + 57
• Leading digit (30 + 50) + (9 + 7)
• Compensation (40 - 1) + 57
• Compensation (40 + 57) - 1
• Break and Bridge (39 + 50) + 7
• Compatible Numbers (39 + 51) + 6
The name of the method is not important
• Put down your pencil
• 68 + 74
• How did you do this?
• How might children do this?
You try…• 23 + 96
• 489 + 723
Estimation• Get a QUICK answer that is close but
not exact!
You will have 5 seconds
• 382 - 147
Estimation• 382 - 147• Actual answer: 235• Ways to estimate:• 380 - 150 = 230• 400 - 150 - 20 = 230• 375 - 150 = 225• 385 - 145 = 240• 390 - 140 = 250
You try:• 45 + 87
• 391 + 1472
Estimation vs. Exact Answer
• Are the exact values of the addends given?
• Is the exact value of the sum required?• In general: changing values (like
population), measurement values (like distance), and predictions (like 35% chance of rain) are estimates
Rounding• When you estimate, you are rounding
to the nearest ten, hundred, million, etc.
• If you round up, you are making an overestimation.
• If you round down, you are making an underestimation.
A problem:• I am thinking of 3 numbers whose sum is
greater than 70.• Look at each statement below. Mark it as
true or false. Be ready to explain why.• All three numbers are greater than 20.• If two of the number are less than 20, the
other must be greater than 20.
Explain the math• 348
+ 472 10 11 7
• 820
Explain the math• 471
+ 299 10 160 600
• 770• How is this different from the previous
problem?
Explain why the child made the mistake
• 341 + 287 is the same as 340 + 290 + 7 + 3
• 749 + 684 is the same as 700 + 600 + 49 + 1 + 84 + 16
• 322 + 468 is the same as 320 + 460
• Would the mistake have been made if manipulatives had been used? Explain.
Assignment• Section 3.1 p. 150-151
#5, 6, 10, 24