By Raymond M. Smullyan
A variety of puzzles facing be aware play and good judgment, arithmetic and philosophy, that includes Alice and the creatures of Wonderland
Read or Download Alice in puzzle-land : a Carrollian tale for children under eighty PDF
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Additional resources for Alice in puzzle-land : a Carrollian tale for children under eighty
It does not work so well when you need to round up more than two digits because the subtraction portion of the problem gets out of hand. As it is, you may prefer to stick with the addition method. Personally, I only use the addition method because in the time spent deciding which method to use, I could have already done the calculation! So that you can perfect your technique we strongly recommend practicing more 2-bY-l multiplication problems. Below are 20 problems for you to tackle. We have supplied you with the answers in the back of the book, including a breakdown of each component of the multiplication.
Then I pause to compute 60 + 72 = 132. Because I have already carried, I say only the last two digits, "... " And there is the answer: 5832. The next two problems require you to carry two numbers each, so they may take you longer than those you have already done. But with practice you will get faster: 489 (400 X 400 X 7 = 80x7= 7 2800 + 560 3360 9x7= + 63 3423 + 80 + 9) PRODUCTS OF A MISSPENT YOUTH: BASIC MULTIPLICATION 27 224 (200 x 200 x 9 = 20 x 9 = + 20 + 4) 9 1800 + 180 1980 4x9= + 36 2016 When you are first tackling these problems, repeat the answers to each part out loud as you compute the rest.
2-DIGIT SUHfRACTION For 2-digit subtraction, as in addition, your goal is to keep simplifying the problem until you are reduced to subtracting a 1-digit number. Let's begin with a very simple subtraction problem: 86 - 25 (20 + 5) After each step, you arrive at a new and smaller subtraction problem. Begin by subtracting: 86 - 20 = 66. Your problem becomes 66 5 = 61, your final answer. The problem can be diagrammed this way: 86 - 20 66 - 5 -25~-5-i = 61 Of course, subtraction problems are considerably easier when they do not involve borrowing.