Calculate a Fraction of a Whole Number

Transcription

1 Calculate a Fraction of a Whole Number Objective: Calculate a fraction of a whole number Terms and Conditions To the best of the producer's knowledge, the academic content of this resource is accurate but errors and omissions may be present and Brain-Cells: E.Resources Ltd cannot be held responsible for these or any lack of success experienced by individuals or groups or other parties using this material. The presentation is intended as support material for National Curriculum mathematics and is not a comprehensive pedagogy of all the designated topics. The copyright proprietor has licensed the PowerPoint version of the presentation for the purchaser s use as a personal learning aid and prohibits copying or reproduction in part or whole or its use as a teaching aid or resources in any school or college that has not purchased the presentation or the publication of the material on the Internet or other media without the written permission of Brain-Cells: E.Resouces Ltd. Whilst, the Flash version may be freely viewed on it may not be downloaded for any commercial use without the written permission of Brain-Cells: E.Resouirces Ltd.

2 A baker has a tray of 12 cakes. What is ½ of 12? What is ¼ of 12? What is ¾ of 12?

3 A baker has a tray of 12 cakes. What is ½ of 12? What is ¼ of 12? What is ¾ of 12? 6 3 9

4 What fraction of these shapes are shaded?

5 What fraction of these shapes are shaded? 1/3 1/2 1/4 3/4 1/3 2/3

6 We often want to find a fraction of a whole number. What, for example, would be ⅝ of 32? To do this and other similar problems, we need a method. The next couple of slide shows a method for doing these types of problems.

7 If we wanted to find ¾ of 24, here is a method of how this could be found: First find a ¼ of 24 You do this by dividing 24 by = 6 Calculate ¾ of = 6 6 x 3 = 18 ¾ of 24 = 18 You want three quarters, so you multiply 6 by = 18

8 We can apply our method to other similar problems. If we wanted to find ⅝ of 32, here is how to do it: First find find a ⅛ of of You You do do this this by by dividing by by = 4 Calculate ⅝ of = 4 4 x 5 = 20 ⅝ of 32 = 20 You You want five five eighths, so so you you multiply 4 by by = 20 20

9 The method can be used to find the fraction of any amount. Here is an explanation of why it works: Multiply by 5 finds the value of ⅝ First find a ⅛ of 32 You do this by dividing 32 by = 4 Calculate ⅝ of = 4 4 x 5 = 20 ⅝ of 32 = 20 Divide by 8 finds the value of ⅛ You want five eighths, so you multiply 4 by = 20

10 Now, you get the chance to have a go. Try these a. 1/2 of 16 b. 3/4 of 16 c. 2/3 of 15 d. 3/5 of 10 e. 2/3 of 30 f. 1/4 of 32 g. 3/4 of 28 h. 3/5 of 20 i. 1/8 of 16 j. 2/3 of 12 k. 2/5 of 20 l. 2/3 of 21 m. 3/4 of 20 n. 3/5 of 50 o. 3/4 of 16 p. 2/5 of 35 q. 3/8 of 16 r. 3/4 of 36 s. 2/5 of 40 t. 2/3 of 27 u. 3/4 of 60 v. 3/8 of 32 w 2/3 of 24 x. 1/4 of 72 y. 3/4 of 84 z. 3/5 of 60 θ. 3/8 of 72

11 Now, you get the chance to have a go. Try these a. 1/2 of 16 8 j. 2/3 of 12 8 s. 2/5 of b. 3/4 of k. 2/5 of 20 8 t. 2/3 of c. 2/3 of l. 2/3 of u. 3/4 of d. 3/5 of 10 6 m. 3/4 of v. 3/8 of e. 2/3 of n. 3/5 of w 2/3 of f. 1/4 of 32 8 o. 3/4 of x. 1/4 of g. 3/4 of p. 2/5 of y. 3/4 of h. 3/5 of q. 3/8 of 16 6 z. 3/5 of i. 1/8 of 16 2 r. 3/4 of θ. 3/8 of 72 27