Download
1 / 18
180 likes | 308 Vues
Managing a grocery budget can be challenging, especially when you need to keep track of how much you're spending. This guide provides strategies for estimating and rounding to stay within your $20 limit while ensuring you meet the $10 threshold for discounts on school supplies. Discover effective methods to monitor your cart's total without the stress of abandoning items. With practical homework and exercises to reinforce understanding of place value and algorithms, you'll become a savvy shopper in no time!
E N D
Week 4 Shopping: You have a strict budget when you are shopping for groceries. If you know that you can’t spend more than $20, how do you keep track of “how much is in your cart” so that you don’t have to put anything back? You need to spend at least $10 to get a discount on school supplies. How do you keep track of how much you’ve spent in order to get the discount?
Agenda • Don’t forget to initial attendance sheet! Homework “key”: a = answer with work, j = justify, s = strategy, e = extend your thinking Homework comment Estimation and Rounding Subtraction
#6, 10Section 3.1 in textbook • Ask yourself… • “Were students applying correct “rules” incorrectly or do they not seem to be using the algorithm at all?” • Are the students not understanding place value or not understanding the algorithm? Is it something else? • “Would students have made any of these mistakes if they were using base 10 blocks?”
Ask yourself… • “If students thought of each number as more than a collection of digits, (e.g., 56 is 5 tens and 6 ones) would these mistakes be made?” • “Do my explanations focus on rules or on the reason why, mathematically, these errors do not produce the correct answer?”
Estimation • Get a QUICK answer that is close but not exact!
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.
You will have 10 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
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.
Subtraction • Vocabulary: • A – B = CA is the minuendB is the subtrahendC is the difference
Try this: • Is A - B = B - A? • 6 - 4 = 4 - 6? • What is true of 6 - 4 and 4 - 6? • One of the worst things we can do is lie to kids: “You can’t take a bigger number away from a smaller number.” Or “You have to put the bigger number first (in the minuend).”
Pictorial Models • Take away • Judy has 7 crosses and gives 2 to Jake. How many does Judy have left?
Pictorial Models • Comparison • Amy has 7 crosses and Andy has 2. How many more crosses than Andy does Amy have?
Homework • Due Friday: Read Section 3.2 • Due Wednesday: • Section 3.2 p. 166-168#1abc, 4, 7cdf, 20, 28ac
