 Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum  MENU          Solutions for Session 3, Part C

See solutions for Problems: C1 | C2 | C3 | C4 | C5 | C6| C7 | C8 | C9 | C10 | C11    Problem C1 The number 48 will come out at the bottom.   Problem C2 Try to undo the steps. The original number was 7.   Problem C3 The order of operations is: multiply by 2, subtract 6, divide by 10, subtract3, divide by 2. Algorithm D is the inverse of Algorithm C, so using 88 as the input for Algorithm D would answer Problem C2.    Problem C4 The huge Algorithm CD doesn't do anything; its output numbers will equal its input numbers.   Problem C5

All of them are possible in multiple ways.

 • 59 = 10 x 5 + 9 • 216 = 6 x 6 x 6 • 15625 = 5 x 5 x 5 x 5 x 5 x 5 • 7280 = 9 x 9 x 9 x 10 - 10 • 0.12345 = [(1 / 9) / 9] x 10   Problem C6 The output will be 4.   Problem C7 Use Algorithm B, which undoes Algorithm A. The input was 8.   Problem C8 Using Algorithm B, the input was 31.   Problem C9    Problem C10 It will leave the number unchanged, since A and B undo each other.   Problem C11 If you can list the algorithm as a series of steps involving unchanging numerical operations (like "add 6"), then they can be undone by an algorithm which performs the inverse operation, and where the steps are performed in reverse order. Unfortunately, some operations do not have inverses, like squaring or throwing a water balloon. Think of Mr. Lewis's rule from Session 2 -- this is a rule that cannot be undone.     Session 3: Index | Notes | Solutions | Video

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