Metric Measures XII. POSITIVE AND NEGATIVE NUMBERS Addition Used in Solving Equations Subtraction Used in Solving Equations XIII. POSITIVE AND NEGATIVE NUMBERS ADVICE TO THE PUPIL Accuracy in arithmetic. Careful writing of figures and neat orderly arrangement of the solution of an example will help you solve your example accurately. Avoid doing "scratch work." Do upon your final paper any computing which you find necessary. Place such computation at the right side of your paper, arranging the main steps of your solution at the left side of the paper. Checking solutions. Even expert computers check the solution of a problem in some way to make certain that the result is correct. You must form the habit of checking your solutions. A first check is to examine the result to determine whether it appears reasonable. Thus if the rent of a house turns out to be $7550 per month, it is likely that a mistake has been made in locating the decimal point, and that the result should be $75.50. The solution should be examined carefully to determine what is the correct result. Other checks will appear as you study the book. Speed in computing is chiefly a result of long practice, and partly a result of the use of short methods of computing. Some of these short methods you may know; others are new to you. In this grade you should seek such short cuts and use them whenever possible. JUNIOR HIGH SCHOOL MATHEMATICS BOOK II I. SHORT METHODS OF COMPUTING 1. Devices used in adding. a. Check addition by adding a second time but in the opposite direction, or by casting out nines (see p. 233). b. When adding a column of figures name only the results, even in your mind. c. When adding a column of figures, group and add at sight integers whose sum is 10. These integers may not be close together in the column. Similarly, if 3 and 6 are together in a column, do not first add 3 and then 6; but, instead, at once add 9. |