\frac{1}{5}+\frac{2}{11}

1. Mínimo común múltiplo de los denominadores: \text{mcm}(5,11)=55.
2. Se amplifica: \frac{1}{5}=\frac{11}{55} y \frac{2}{11}=\frac{10}{55}.
3. Se suman los numeradores: \frac{11+10}{55}=\frac{21}{55}.

\frac{8}{21}+\frac{2}{7}

1. \text{mcm}(21,7)=21.
2. \frac{2}{7}=\frac{6}{21}.
3. \frac{8+6}{21}=\frac{14}{21}=\frac{2}{3}.

\frac{17}{24}+\frac{5}{12}

1. \text{mcm}(24,12)=24.
2. \frac{5}{12}=\frac{10}{24}.
3. \frac{17+10}{24}=\frac{27}{24}=\frac{9}{8}.

\frac{4}{15}+\frac{1}{6}

1. \text{mcm}(15,6)=30.
2. \frac{4}{15}=\frac{8}{30} y \frac{1}{6}=\frac{5}{30}.
3. \frac{8+5}{30}=\frac{13}{30}.

\frac{5}{6}+\frac{3}{8}

1. \text{mcm}(6,8)=24.
2. \frac{5}{6}=\frac{20}{24} y \frac{3}{8}=\frac{9}{24}.
3. \frac{20+9}{24}=\frac{29}{24}.

\frac{2}{3}-\frac{2}{5}

1. \text{mcm}(3,5)=15.
2. \frac{2}{3}=\frac{10}{15} y \frac{2}{5}=\frac{6}{15}.
3. \frac{10-6}{15}=\frac{4}{15}.

\frac{7}{4}-\frac{1}{6}

1. \text{mcm}(4,6)=12.
2. \frac{7}{4}=\frac{21}{12} y \frac{1}{6}=\frac{2}{12}.
3. \frac{21-2}{12}=\frac{19}{12}.

\frac{1}{2}-\frac{1}{6}

1. \text{mcm}(2,6)=6.
2. \frac{1}{2}=\frac{3}{6}.
3. \frac{3-1}{6}=\frac{2}{6}=\frac{1}{3}.

\frac{5}{6}-\frac{2}{15}

1. \text{mcm}(6,15)=30.
2. \frac{5}{6}=\frac{25}{30} y \frac{2}{15}=\frac{4}{30}.
3. \frac{25-4}{30}=\frac{21}{30}=\frac{7}{10}.

\frac{5}{12}-\frac{1}{6}

1. \text{mcm}(12,6)=12.
2. \frac{1}{6}=\frac{2}{12}.
3. \frac{5-2}{12}=\frac{3}{12}=\frac{1}{4}.

Desafío final

52=\square+\square

1. Se buscan dos números que sumen 52.
2. Una descomposición posible es 52=50+2.

Respuesta: 52=50+2 (también sirve 52=26+26, 52=40+12, etc.).