Mathematics lesson: MultiplicationTeacher: Mona, Delhi. Mathematics is a wonderful, elegant, and exceedingly useful language. It has its own vocabulary and syntax, its own verbs, nouns, and modifiers, and its own dialects and patois. It is used brilliantly by some, poorly by others. Some of us fear to pursue its more esoteric uses, while a few of us wield it like a sword to attack and conquer income tax forms or masses of data that resist the less courageous. This article does not guarantee to turn you into a Leibniz, or put you on stage as Professor Algebra, but it will, I hope, bring you a new, exciting, and even entertaining view on Multiplication. In this article, you will learn to do multiplication in your head faster than you ever thought possible. After practicing the methods in this article for just a little while, your ability to work with multiplication will increase dramatically. With even more practice, you will be able to perform many calculations faster than someone using a calculator. Multiplying Number by Eleven: Let’s begin with how to multiply any two-digit number by eleven in your head. Consider the problem:45 X 11To solve this problem, simply add the digits, 4+5 = 9, put the 9 between the 4 and the 5, and there is your answer, 495. What could be easier? Now you try:53 X 11Since 5 + 3 = 8, your answer is simply, 583. Now before you get too excited, suppose the problem is67 X 11 Although 6+7= 13, the answer is NOT 6137, as before, the 3 goes in between the numbers, but the 1 needs to be added to the 6 to get the correct answer: 737 Now, if you tell a friend or teacher that you can multiply, in your head, any two-digit number by eleven. You will be amazed at the reaction you get. Now, question is, Can we use this method for multiplying three-digit numbers (or larger) by eleven? Answer is yes, you can, for instance, for the problem 314 X 11; the answer still begins with 3 and ends with 4. Since 3+1=4, and 1+4= 5, the answer is 3454. More you practice more you comfortable with multiplying any number with eleven. Simple Methods for 2-BY-2 Multiplication: When squaring two-digit numbers, the method is always the same. When multiplying two-digit numbers, however, you can use lots of different methods to arrive at the same answer. For me, this is where the fun begins. I will tell you about “addition method,” and similarly one can use “subtraction method” to solve all 2-by-2 multiplication problems. The Addition Method: To use the addition method to multiply any two two-digit numbers, all you need to do is perform two 2-by-1 multiplication problems and add the results together. For example to multiple 42 by 46 one can use following steps:46X 42 (40+2)40X46 = 18402X46 = + 92--------1932 Here you break up 42 into 40 and 2, two numbers that are easy to multiply. Then you multiply 40X46, which is just 4X46 with a 0 attached, or 1840. Then you multiply 2X46= 92. Finally, you add 1840+92= 1932.Here’s another way to do the same problem:46 (40+6)X 4240X42 = 16806X42 = +252--------1932 The catch here is that multiplying 6X42 is harder to do than multiplying 2X46, as in the first problem. Moreover, adding 1680+252 is more difficult than adding 1840+92. So how do you decide which number to break up? I try to choose the number that will produce the easier addition problem. In most cases—but not all—you will want to break up the number with the smaller last digit because it usually produces a smaller second number for you to add. Following are some of the tips on breaking up the number:• If both numbers end in the same digit, you should break up the larger number• Break the number which ends with 1• If one number is much larger than the other, it often pays to break up the larger number, even if it has a larger last digit• When you multiply a number in the fifties by an even number, you’ll want to break up the number in the fifties Subtraction … [Read more...]