FRACTIONS IN COMMON USE The following fractions are the ones that we usually have to add or subtract in real problems that arise in everyday affairs. 1 1 1 1 2 1 1 § 7 1 § ¦ ¦ § 7 8 ADDING MIXED NUMBERS ADDING MIXED NUMBERS 179 1. James worked 24 hr. one day, 14 hr. the next, and 23 hr. the next. Find how long he worked. 214 12 21/3 61/12 By inspection, all the fractions may be changed to 12ths. In adding think, " 3, 6, and 4 are 13," and remember they are 12ths. Think, “ 13 = 11" Write; carry 1. By carrying such mental changes in mind instead of writing them much work is saved. If 2. Mary needs 33 yd. of gingham for a dress, her sister needs 4 yd., and her mother needs 24 yd. for an apron. bought in one piece, how much must be bought? 334 412 214 1012 In such problems, do not change to 2, but think, "3+1 = 1. So the sum of the fractions is 11." Write; carry 1. This saves work. 3. For some curtains Helen needed three pieces, one containing 24 yd., one containing 23 yd., and one 12 yd. If bought in one piece, how much must she call for? 216 213 134 614 Do not change all three fractions to 12ths, but think, " + 1 ; 1 + 2 = 11." = Write; carry 1. This saves work. In adding fractions, first see if certain fractions may not be added and reduced at sight, and their sum added to other fractions. Never waste time in changing all the fractions to the same denominator except when it is simpler than to add groups as in problem 3. Add, using the method that seems to you to make the least SUBTRACTING MIXED NUMBERS 1. Frank weighed 871 lb. in June and 962 lb. in SepHow much did he gain? tember. SUBTRACTING MIXED NUMBERS 181 7. Walter weighed 852 lb. in June and 98 lb. in September. How much did he gain? Since there is no fraction in the larger number, think," and make 1." Write 1. Carry 1. 98 8534 Then think, "6 and 2 are 8." Write 2. 1214 Check by finding 121 + 85. 13. Ralph weighed 863 lb. in June and 98 lb. in September. How much did he gain? Here is less than . So think, " and 1 2. 9812 make 1." Then think," and make 3." 8634 Write 3. Carry 1. 'Then think, "7 and 1 are 1134 8." Write 1. Check by finding 113 + 863. |