1. จงหาผลบวก
1) \(\mathsf{\frac{7}{11} + (-\frac{5}{11})}\)
วิธีทำ
\(\mathsf{\frac{7}{11} + (-\frac{5}{11})}\)
= \(\mathsf{\frac{7 \,+\, (-5)}{11}}\)
= \(\mathsf{\frac{2}{11}}\)
ตอบ \(\mathsf{\frac{2}{11}}\)
2) \(\mathsf{\frac{5}{6} + (-\frac{7}{12})}\)
วิธีทำ
\(\mathsf{\frac{5}{6} + (-\frac{7}{12})}\)
= \(\mathsf{(\frac{5}{6} \times \frac{2}{2}) + (-\frac{7}{12})}\)
= \(\mathsf{\frac{10}{12} + (-\frac{7}{12})}\)
= \(\mathsf{\frac{10 \,+\, (-7)}{12}}\)
= \(\mathsf{\frac{3}{12}}\)
= \(\mathsf{\frac{1}{4}}\)
ตอบ \(\mathsf{\frac{1}{4}}\)
3) \(\mathsf{(-2\frac{1}{9}) + (-\frac{8}{9})}\)
วิธีทำ
\(\mathsf{(-2\frac{1}{9}) + (-\frac{8}{9})}\)
= \(\mathsf{(-\frac{19}{9}) + (-\frac{8}{9})}\)
= \(\mathsf{\frac{(-19) \,+\, (-8)}{9}}\)
= \(\mathsf{-\frac{27}{9}}\)
= -3
ตอบ -3
4) \(\mathsf{-1\frac{4}{15} + \frac{3}{5}}\)
วิธีทำ
\(\mathsf{-1\frac{4}{15} + \frac{3}{5}}\)
= \(\mathsf{-\frac{19}{15} + \frac{3}{5}}\)
= \(\mathsf{-\frac{19}{15} + (\frac{3}{5} \times \frac{3}{3})}\)
= \(\mathsf{-\frac{19}{15} + \frac{9}{15}}\)
= \(\mathsf{\frac{-19 \,+\, 9}{15}}\)
= \(\mathsf{-\frac{10}{15}}\)
= \(\mathsf{-\frac{2}{3}}\)
ตอบ \(\mathsf{-\frac{2}{3}}\)
5) \(\mathsf{(-\frac{5}{6}) + (-2\frac{1}{3})}\)
วิธีทำ
\(\mathsf{(-\frac{5}{6}) + (-2\frac{1}{3})}\)
= \(\mathsf{(-\frac{5}{6}) + (-\frac{7}{3})}\)
= \(\mathsf{(-\frac{5}{6}) + (-\frac{7}{3} \times \frac{2}{2})}\)
= \(\mathsf{(-\frac{5}{6}) + (-\frac{14}{6})}\)
= \(\mathsf{\frac{(-5) \,+\, (-14)}{6}}\)
= \(\mathsf{-\frac{19}{6}}\)
= \(\mathsf{-3\frac{1}{6}}\)
ตอบ \(\mathsf{-3\frac{1}{6}}\)
6) \(\mathsf{-5 + (-\frac{3}{7})}\)
วิธีทำ
\(\mathsf{-5 + (-\frac{3}{7})}\)
= \(\mathsf{(-\frac{5}{1} \times \frac{7}{7}) + (-\frac{3}{7})}\)
= \(\mathsf{-\frac{35}{7} + (-\frac{3}{7})}\)
= \(\mathsf{\frac{(-35) \,+\, (-3)}{7}}\)
= \(\mathsf{-\frac{38}{7}}\)
= \(\mathsf{-5\frac{3}{7}}\)
ตอบ \(\mathsf{-5\frac{3}{7}}\)
7) \(\mathsf{1\frac{5}{6} + (-\frac{8}{9})}\)
วิธีทำ
\(\mathsf{1\frac{5}{6} + (-\frac{8}{9})}\)
= \(\mathsf{\frac{11}{6} + (-\frac{8}{9})}\)
= \(\mathsf{(\frac{11}{6} \times \frac{6}{6}) + (-\frac{8}{9} \times \frac{4}{4})}\)
= \(\mathsf{\frac{66}{36} + (-\frac{32}{36})}\)
= \(\mathsf{\frac{66 \,+\, (-32)}{36}}\)
= \(\mathsf{\frac{34}{36}}\)
= \(\mathsf{\frac{17}{18}}\)
ตอบ \(\mathsf{\frac{17}{18}}\)
8) \(\mathsf{-2\frac{7}{11} + 1\frac{5}{22}}\)
วิธีทำ
\(\mathsf{-2\frac{7}{11} + 1\frac{5}{22}}\)
= \(\mathsf{-\frac{29}{11} + \frac{27}{22}}\)
= \(\mathsf{(-\frac{29}{11} \times \frac{2}{2}) + \frac{27}{22}}\)
= \(\mathsf{-\frac{58}{22} + \frac{27}{22}}\)
= \(\mathsf{\frac{(-58) \,+\, 27}{22}}\)
= \(\mathsf{-\frac{31}{22}}\)
= \(\mathsf{-2\frac{9}{22}}\)
ตอบ \(\mathsf{-2\frac{9}{22}}\)
9) \(\mathsf{2\frac{7}{12} + (-3\frac{3}{8})}\)
วิธีทำ
\(\mathsf{2\frac{7}{12} + (-3\frac{3}{8})}\)
= \(\mathsf{\frac{31}{12} + (-\frac{27}{8})}\)
= \(\mathsf{(\frac{31}{12} \times \frac{2}{2}) + (-\frac{27}{8} \times \frac{3}{3})}\)
= \(\mathsf{\frac{62}{24} + (-\frac{81}{24})}\)
= \(\mathsf{\frac{62 \,+\, (-81)}{24}}\)
= \(\mathsf{-\frac{19}{24}}\)
ตอบ \(\mathsf{-\frac{19}{24}}\)
10) \(\mathsf{-5\frac{1}{14} + (-2\frac{4}{21})}\)
วิธีทำ
\(\mathsf{-5\frac{1}{14} + (-2\frac{4}{21})}\)
= \(\mathsf{-\frac{71}{14} + (-\frac{46}{21})}\)
= \(\mathsf{(-\frac{71}{14} \times \frac{3}{3}) + (-\frac{46}{21} \times \frac{2}{2})}\)
= \(\mathsf{-\frac{213}{42} + (-\frac{92}{42})}\)
= \(\mathsf{\frac{(-213) \,+\, (-92)}{42}}\)
= \(\mathsf{-\frac{305}{42}}\)
= \(\mathsf{-7\frac{11}{42}}\)
ตอบ \(\mathsf{-7\frac{11}{42}}\)