  |
||||||
|
|
I hope by now you have developed some feeling for different methods of doing multiplications quickly.
In this example, see how the compensation in multiplication makes the job simple! Let us now try to find the product of 48 x 45, given as a second problem. You may try to use all the methods. However, I will discuss only the application of compensation. We can do the same task by performing 240 x 9 or 8 x 270. I am writing only these two out of many other combinations, as these are the two easier forms of multiplication. We can choose either, as they have the same difficulty level. This multiplication can be mentally calculated as 2160. Coming to the third problem, which was 128 x 12, we find that the distributive property of multiplication on addition is a better choice. First, we change the order of numbers in the problem as 12 x 128 and then solve it as 12 x 128 = 12 x 100 + 12 x 20 + 12 x 8. Which is: 1200 + 240 = 1440 + 96 = 1536. The fourth problem was 62 x 35. This can be transformed into an easier form as 310 x 7. Guess how? The final answer can now be obtained easily as 2170. The last problem was 64 x 25. We can solve it as 60 x 25 + 4 x 25. Which works to 1500 + 100 or 1600. The other way is to change it to a simple product as 16 x 100. How? Divide 64 by 4 and multiply 25 by 4! And you can instantly arrive at the final answer as 1600! Which of these two do you find easier? Both appear equally easy! Choose either! So, you might come across problems when either of the distributive property or the compensation in multiplication proves equally useful and you can try any one. Please notice that in solving most of the problems above we have used the rule of order in multiplication instinctively to make the multiplication convenient! Also, see how we have been using the distributive property of multiplication on addition in the conventional method without even being aware of it! Practice alone will tell you which rule is most suitable to handle a particular multiplication. I have found that if in the given multiplication either the multiplicand or the multiplier is less than ten and the remaining number is greater than ten, distributive property seems to be appropriate. Whereas, if there is a chance that after multiplying the multiplicand or the multiplier by a number the product is a round number (number ending in one or more zeros) and the remainder of the multiplicand/multiplier gets divided by that number evenly, then the use of compensation in multiplication is convenient. (Since I have not yet said anything about division, we might say that remainder of the multiplicand/multiplier should be in the multiplication table of that number.)
Go To Page: 1 2
The copyright of the article Applying multiplication rules (Part II)
in Math for Kids is owned by Vidya Narayan Wadadekar . Permission to republish Applying multiplication rules (Part II)
in print or online must be granted by the author in writing.
|
|||||
|
|
||||||
