How to calculate _ + _ + _ + 30

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63 3 Calculating with Fractions Workbook page 30 You will always find a common denominator if you multiply the given denominators together. Does this rule always make sense? Try it out with the examples and present your thoughts to the class. a) 2 _ 3 + 2 _ 5 b) 2 _ 9 + 4 _ 9 c) 2 _ 3 + 1 _ 6 d) 3 _ 4 + 2 _ 5 e) 7 _ 10 + 5 _ 8 f) 3 _ 4 + 2 _ 9 g) 11 _ 15 + 2 _ 15 h) 1 _ 4 + 7 _ 8 i) 2 _ 7 + 4 _ 5 j) 5 _ 6 + 3 _ 8 Calculate. Find the lowest possible common denominator. a) 1 _ 6 + 1 _ 3 b) 3 _ 4 + 1 _ 6 c) 7 _ 30 + 5 _ 12 d) 5 _ 12 + 1 _ 6 e) 5 _ 6 + 1 _ 9 f) 7 _ 33 + 4 _ 6 g) 2 _ 9 + 2 _ 3 h) 4 _ 9 + 5 _ 12 Lukas and Alex solve the addition 2 1 _ 4 + 3 2 _ 3. Lukas calculates like this: Alex calculates like this: a) Discuss the solutions of Lukas and Alex. What is different b) Which strategy do you find more skillful? Justify your decision. Try out the strategies of Lukas and Alex in the following tasks: a) 3 3 _ 4 + 2 1 _ 5 b) 4 3 _ 5 + 7 9 _ 10 c) 15 7 _ 9 + 12 5 _ 6 d) 4 7 _ 8 + 6 3 _ 5 Between which natural numbers does the result lie? Example: 3 1 _ 4 + 2 1 _ 4 is between 5 and 6. a) 5 3 _ 4 + 6 3 _ 4 b) 7 1 _ 5 + 3 4 _ 5 c) 10 5 _ 6 + 10 2 _ 3 d) 2 7 _ 12 + 10 1 _ 2 e) 13 9 _ 11 + 11 9 _ 13 f) 4 17 _ 18 + 9 17 _ 28 Invent three tasks each with the result between a) 3 and 4 b) 9 and 10 lies. Control through an invoice. Complete the wall of numbers. I1 H1, 2 K2 247 I1 H2 K1 248 I1 H2–4 K3 249 2 1 _ 4 + 3 2 _ 3 = 8 _ 4 + 1 _ 4 + 9 _ 3 + 2 _ 3 = = 24 _ 12 + 3 _ 12 + 36 _ 12 + 8 _ 12 = = 71 _ 12 = 5 11 _ 12 2 1 _ 4 + 3 2 _ 3 = 2 + 1 _ 4 + 3 + 2 _ 3 = = 2 + 3 + 3 _ 12 + 8 _ 12 = = 5 + 11 _ 12 = 5 11 _ 12 I1 H2 K2 250 I1 H2 K2 251 I1 H2 K2 252 I1 H2 K2 253 _ 1 5 _ 1 2 _ 3 4 3 _ 11 60 Tip The value of a stone is determined from the sum of the two stones below. + Master copy v5f7yf For testing purposes only - property of the publisher öbv

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