XXXI A Speed Test in Checking Addition Find out in 10 min. why this boy's paper was marked 75%. Be sure to check your own answer if it does not agree with the boy's answer which is printed below each example. A Speed Test in Checking Division Check this work in 8 min. CHECKING SPEED TESTS 23 XXXIII Checking a Subtraction Speed Test Check these answers in 4 min. If your result does not agree with the one here given, prove it. This girl's paper was marked 80. Find out by solving all the examples whether the paper was marked properly. Each correct answer is worth 10. Prove your answer if it does not agree with the one here SPEED AND ACCURACY IN COMPUTATION THROUGH SHORT METHODS A pupil whose accuracy in computation is not better than 90%, wrong once in ten, should not hope to hold any position requiring much computing. Business men will not employ careless computers for positions of responsibility. Short methods in operations are not only a time saving device, but they are also a means of securing greater accuracy. A pupil who learns to get a required result by two operations which formerly required four has reduced through the short method his chances at error by at least 50%. I. By Group Adding. In Addition 1. Grouping the addition facts. In column addition you should use in the manner here shown the addition facts already learned. 356 482 769 851 Adding the 1st column, think 17, 27, 35. Write 5. Write 1. 678 479 Adding the 3rd column, think 14, 29, 36. Write 36. Time yourself to-day. 2. Grouping by 100's. IN ADDITION 25 In short two-figure columns it is often convenient to group the numbers which make 100. in this way. to-morrow. Try these examples In short examples sometimes it is possible to add three columns at a time by grouping those numbers which make 100's or 150's. Try these examples in this way. II. By Line Adding. 1. Adding two numbers without pencil. Add to the first number the largest decade of the second. Then to this sum add the units of the second. 45+38 ? Think 45, 75, 83. = 2. Line and column adding. It is sometimes necessary to add columns horizontally in preparing statistical reports, comparative statements, etc. Add by lines and then by columns. Check your work by finding the value of ?? in two ways. These sales were made in the different departments of a store. Find the value of all the ?. Tell the meaning of each. Department Dry Goods... Groceries. Clothing.. Furniture... Mon. Tues. Wed. Thur. Fri. Sat. Totals ? .?. 2. ? Boots and Shoes... 257.12 284.32 213.46 312.30 262.49 385.72 ? |