Краткий ответ:
При
a = 1 6 a = \frac{1}{6}
:
1 6 + 5 12 = 2 12 + 5 12 = 7 12 ≤ 2 1 3 \frac{1}{6} + \frac{5}{12} = \frac{2}{12} + \frac{5}{12} = \frac{7}{12} \leq 2 \frac{1}{3}
7 12 + 1 4 = 7 12 + 3 12 = 10 12 = 5 6 \frac{7}{12} + \frac{1}{4} = \frac{7}{12} + \frac{3}{12} = \frac{10}{12} = \frac{5}{6}
При
a = 1 3 a = \frac{1}{3}
:
1 3 + 5 12 = 4 12 + 5 12 = 9 12 = 3 4 ≤ 2 1 3 \frac{1}{3} + \frac{5}{12} = \frac{4}{12} + \frac{5}{12} = \frac{9}{12} = \frac{3}{4} \leq 2 \frac{1}{3}
3 4 + 1 4 = 4 4 = 1 \frac{3}{4} + \frac{1}{4} = \frac{4}{4} = 1
При
a = 1 2 a = \frac{1}{2}
:
1 2 + 5 12 = 6 12 + 5 12 = 11 12 ≤ 2 1 3 \frac{1}{2} + \frac{5}{12} = \frac{6}{12} + \frac{5}{12} = \frac{11}{12} \leq 2 \frac{1}{3}
11 12 + 1 = 11 12 + 3 12 = 14 12 = 1 1 6 \frac{11}{12} + 1 = \frac{11}{12} + \frac{3}{12} = \frac{14}{12} = 1 \frac{1}{6}
При
a = 7 12 a = \frac{7}{12}
:
7 12 + 5 12 = 12 12 = 1 ≤ 2 1 3 \frac{7}{12} + \frac{5}{12} = \frac{12}{12} = 1 \leq 2 \frac{1}{3}
1 + 1 4 = 5 4 = 1 1 4 1 + \frac{1}{4} = \frac{5}{4} = 1 \frac{1}{4}
при
a = 5 8 a = \frac{5}{8}
:
5 8 + 5 12 = 15 24 + 10 24 = 25 24 = 1 1 24 ≤ 2 1 3 ⇒ подходит \frac{5}{8} + \frac{5}{12} = \frac{15}{24} + \frac{10}{24} = \frac{25}{24} = 1 \frac{1}{24} \leq 2 \frac{1}{3} \Rightarrow \text{подходит}
1 1 24 + 1 4 = 6 24 + 1 24 = 7 24 + 1 = 2 7 24 1 \frac{1}{24} + \frac{1}{4} = \frac{6}{24} + \frac{1}{24} = \frac{7}{24} + 1 = 2 \frac{7}{24}
при
a = 3 4 a = \frac{3}{4}
:
3 4 + 5 12 = 9 12 + 5 12 = 14 12 = 1 1 6 ≤ 2 1 3 ⇒ подходит \frac{3}{4} + \frac{5}{12} = \frac{9}{12} + \frac{5}{12} = \frac{14}{12} = 1 \frac{1}{6} \leq 2 \frac{1}{3} \Rightarrow \text{подходит}
1 1 6 + 1 4 = 2 12 + 3 12 = 5 12 + 2 = 2 5 12 1 \frac{1}{6} + \frac{1}{4} = \frac{2}{12} + \frac{3}{12} = \frac{5}{12} + 2 = 2 \frac{5}{12}
при
a = 1 2 3 a = 1 \frac{2}{3}
:
1 2 3 + 5 12 = 8 12 + 5 12 = 13 12 + 1 = 2 1 12 ≤ 2 1 3 ⇒ подходит 1 \frac{2}{3} + \frac{5}{12} = \frac{8}{12} + \frac{5}{12} = \frac{13}{12} + 1 = 2 \frac{1}{12} \leq 2 \frac{1}{3} \Rightarrow \text{подходит}
2 1 12 + 1 4 = 2 12 + 3 12 = 5 12 + 3 = 3 5 12 2 \frac{1}{12} + \frac{1}{4} = \frac{2}{12} + \frac{3}{12} = \frac{5}{12} + 3 = 3 \frac{5}{12}
при
a = 5 6 a = \frac{5}{6}
:
5 6 + 5 12 = 10 12 + 5 12 = 15 12 = 1 1 4 ≤ 2 1 3 ⇒ подходит \frac{5}{6} + \frac{5}{12} = \frac{10}{12} + \frac{5}{12} = \frac{15}{12} = 1 \frac{1}{4} \leq 2 \frac{1}{3} \Rightarrow \text{подходит}
2 1 4 + 1 4 = 2 4 + 3 4 = 5 4 + 2 = 3 1 2 2 \frac{1}{4} + \frac{1}{4} = \frac{2}{4} + \frac{3}{4} = \frac{5}{4} + 2 = 3 \frac{1}{2}
при
a = 1 11 12 a = 1 \frac{11}{12}
:
1 11 12 + 5 12 = 16 12 + 1 = 2 1 3 ≤ 2 1 3 ⇒ подходит 1 \frac{11}{12} + \frac{5}{12} = \frac{16}{12} + 1 = 2 \frac{1}{3} \leq 2 \frac{1}{3} \Rightarrow \text{подходит}
2 1 3 + 1 2 = 4 12 + 3 12 + 3 = 3 7 12 2 \frac{1}{3} + \frac{1}{2} = \frac{4}{12} + \frac{3}{12} + 3 = 3 \frac{7}{12}
при
a = 2 a = 2
:
2 + 5 12 = 2 5 12 > 2 1 3 ⇒ не подходит 2 + \frac{5}{12} = 2 \frac{5}{12} > 2 \frac{1}{3} \Rightarrow \text{не подходит}
2 5 12 − 5 6 = 17 12 − 10 12 = 7 12 2 \frac{5}{12} — \frac{5}{6} = \frac{17}{12} — \frac{10}{12} = \frac{7}{12}
при
a = 23 24 a = \frac{23}{24}
:
23 24 + 5 12 = 10 24 + 23 24 = 33 24 = 1 9 24 = 2 9 24 > 2 1 3 ⇒ не подходит \frac{23}{24} + \frac{5}{12} = \frac{10}{24} + \frac{23}{24} = \frac{33}{24} = 1 \frac{9}{24} = 2 \frac{9}{24} > 2 \frac{1}{3} \Rightarrow \text{не подходит}
2 19 24 − 5 6 = 43 24 − 20 24 = 23 24
при
a = 2 4 9 a = 2 \frac{4}{9}
:
4 9 + 5 12 = 16 36 + 15 36 = 31 36 , 2 31 36 > 2 1 3 ⇒ нет \frac{4}{9} + \frac{5}{12} = \frac{16}{36} + \frac{15}{36} = \frac{31}{36}, \quad 2 \frac{31}{36} > 2 \frac{1}{3} \Rightarrow \text{нет}
2 31 36 − 5 6 = 31 36 − 30 36 = 1 36 2 \frac{31}{36} — \frac{5}{6} = \frac{31}{36} — \frac{30}{36} = \frac{1}{36}
при
a = 2 7 12 a = 2 \frac{7}{12}
:
7 12 + 5 12 = 12 12 = 1 , 2 + 1 = 3 > 2 1 3 ⇒ нет \frac{7}{12} + \frac{5}{12} = \frac{12}{12} = 1, \quad 2 + 1 = 3 > 2 \frac{1}{3} \Rightarrow \text{нет}
3 − 5 6 = 18 − 5 6 = 13 6 = 2 1 6 3 — \frac{5}{6} = \frac{18 — 5}{6} = \frac{13}{6} = 2 \frac{1}{6}
при
a = 3 1 2 a = 3 \frac{1}{2}
:
1 2 + 5 12 = 6 + 5 12 = 11 12 , 3 + 11 12 = 3 11 12 > 2 1 3 ⇒ нет \frac{1}{2} + \frac{5}{12} = \frac{6 + 5}{12} = \frac{11}{12}, \quad 3 + \frac{11}{12} = 3 \frac{11}{12} > 2 \frac{1}{3} \Rightarrow \text{нет}
3 11 12 − 5 6 = 11 12 − 10 12 = 1 12 , 3 + 1 12 = 3 1 12 3 \frac{11}{12} — \frac{5}{6} = \frac{11}{12} — \frac{10}{12} = \frac{1}{12}, \quad 3 + \frac{1}{12} = 3 \frac{1}{12}
при
a = 3 3 4 a = 3 \frac{3}{4}
:
3 4 + 5 12 = 9 + 5 12 = 14 12 = 1 1 6 , 3 + 7 6 = 4 1 6 > 2 1 3 ⇒ нет \frac{3}{4} + \frac{5}{12} = \frac{9 + 5}{12} = \frac{14}{12} = 1 \frac{1}{6}, \quad 3 + \frac{7}{6} = 4 \frac{1}{6} > 2 \frac{1}{3} \Rightarrow \text{нет}
4 1 6 − 5 6 = 25 − 5 6 = 20 6 = 3 1 3 4 \frac{1}{6} — \frac{5}{6} = \frac{25 — 5}{6} = \frac{20}{6} = 3 \frac{1}{3}
при
a = 3 7 8 a = 3 \frac{7}{8}
:
7 8 + 5 12 = 21 + 10 24 = 31 24 , 3 + 31 24 = 4 7 24 > 2 1 3 ⇒ нет \frac{7}{8} + \frac{5}{12} = \frac{21 + 10}{24} = \frac{31}{24}, \quad 3 + \frac{31}{24} = 4 \frac{7}{24} > 2 \frac{1}{3} \Rightarrow \text{нет}
4 7 24 − 5 6 = 103 − 20 24 = 83 24 = 3 11 24 4 \frac{7}{24} — \frac{5}{6} = \frac{103 — 20}{24} = \frac{83}{24} = 3 \frac{11}{24}
при
a = 4 1 12 a = 4 \frac{1}{12}
:
1 12 + 5 12 = 6 12 = 1 2 , 4 + 1 2 = 4 1 2 > 2 1 3 ⇒ нет \frac{1}{12} + \frac{5}{12} = \frac{6}{12} = \frac{1}{2}, \quad 4 + \frac{1}{2} = 4 \frac{1}{2} > 2 \frac{1}{3} \Rightarrow \text{нет}
4 1 2 − 5 6 = 27 − 10 6 = 17 6 = 2 5 6 4 \frac{1}{2} — \frac{5}{6} = \frac{27 — 10}{6} = \frac{17}{6} = 2 \frac{5}{6}
2 \frac{19}{24} — \frac{5}{6} = \frac{43}{24} — \frac{20}{24} = \frac{23}{24}
при
a = 4 5 8 a = 4 \frac{5}{8}
:
5 8 + 5 12 = 15 24 + 10 24 = 25 24 , 4 + 25 24 = 5 1 24 > 2 1 3 ⇒ не подходит \frac{5}{8} + \frac{5}{12} = \frac{15}{24} + \frac{10}{24} = \frac{25}{24},\quad 4 + \frac{25}{24} = 5 \frac{1}{24} > 2 \frac{1}{3} \Rightarrow \text{не подходит}
5 1 24 − 5 6 = 25 24 − 20 24 = 5 24 + 3 = 3 5 24 5 \frac{1}{24} — \frac{5}{6} = \frac{25}{24} — \frac{20}{24} = \frac{5}{24} + 3 = 3 \frac{5}{24}
при
a = 5 7 12 a = 5 \frac{7}{12}
:
7 12 + 5 12 = 1 , 5 + 1 = 6 > 2 1 3 ⇒ не подходит \frac{7}{12} + \frac{5}{12} = 1,\quad 5 + 1 = 6 > 2 \frac{1}{3} \Rightarrow \text{не подходит}
6 − 5 6 = 5 1 6 6 — \frac{5}{6} = 5 \frac{1}{6}
при
a = 5 3 4 a = 5 \frac{3}{4}
:
3 4 + 5 12 = 9 12 + 5 12 = 14 12 , 5 + 14 12 = 6 1 6 > 2 1 3 ⇒ не подходит \frac{3}{4} + \frac{5}{12} = \frac{9}{12} + \frac{5}{12} = \frac{14}{12},\quad 5 + \frac{14}{12} = 6 \frac{1}{6} > 2 \frac{1}{3} \Rightarrow \text{не подходит}
6 1 6 − 5 6 = 37 6 − 5 6 = 32 6 = 5 1 3 6 \frac{1}{6} — \frac{5}{6} = \frac{37}{6} — \frac{5}{6} = \frac{32}{6} = 5 \frac{1}{3}
Подробный ответ:
при a = 1/6: 1/6 + 5/12 = 2/12 + 5/12 = 7/12, 7/12 ≤ 2 1/3 — да 7/12 + 1/4 = 7/12 + 3/12 = 10/12 = 5/6
при a = 1/3: 1/3 + 5/12 = 4/12 + 5/12 = 9/12 = 3/4, 3/4 ≤ 2 1/3 — да 3/4 + 1/4 = 1
при a = 1/2: 1/2 + 5/12 = 6/12 + 5/12 = 11/12, 11/12 ≤ 2 1/3 — да 11/12 + 1 = 11/12 + 3/12 = 14/12 = 1 1/6
при a = 7/12: 7/12 + 5/12 = 12/12 = 1, 1 ≤ 2 1/3 — да 1 + 1/4 = 5/4 = 1 1/4
при a = 5/8: 5/8 + 5/12 = 15/24 + 10/24 = 25/24 = 1 1/24, 1 1/24 ≤ 2 1/3 — да 1 1/24 + 1/4 = 6/24 + 1/24 = 7/24, 1 + 7/24 = 2 7/24
при a = 3/4: 3/4 + 5/12 = 9/12 + 5/12 = 14/12 = 1 1/6, 1 1/6 ≤ 2 1/3 — да 1 1/6 + 1/4 = 2/12 + 3/12 = 5/12, 2 + 5/12 = 2 5/12
при a = 1 2/3: 1 2/3 + 5/12 = 8/12 + 5/12 = 13/12, 1 + 13/12 = 2 1/12 ≤ 2 1/3 — да 2 1/12 + 1/4 = 2/12 + 3/12 = 5/12, 3 + 5/12 = 3 5/12
при a = 5/6: 5/6 + 5/12 = 10/12 + 5/12 = 15/12 = 1 1/4, 2 1/4 ≤ 2 1/3 — да 2 1/4 + 1/4 = 2/4 + 3/4 = 5/4, 2 + 1 1/2 = 3 1/2
при a = 1 11/12: 1 11/12 + 5/12 = 16/12 + 1 = 2 1/3 ≤ 2 1/3 — да 2 1/3 + 1/2 = 4/12 + 3/12 = 7/12, 3 + 7/12 = 3 7/12
при a = 2: 2 + 5/12 = 2 5/12 > 2 1/3 — нет 2 5/12 − 5/6 = 17/12 − 10/12 = 7/12
при a = 23/24: 23/24 + 5/12 = 10/24 + 23/24 = 33/24 = 1 9/24, 2 9/24 > 2 1/3 — нет 2 19/24 − 5/6 = 43/24 − 20/24 = 23/24
при a = 2 4/9: 4/9 + 5/12 = 16/36 + 15/36 = 31/36, 2 31/36 > 2 1/3 — нет 2 31/36 − 5/6 = 31/36 − 30/36 = 1/36
при a = 2 7/12: 7/12 + 5/12 = 12/12 = 1, 2 + 1 = 3 > 2 1/3 — нет 3 − 5/6 = 18/6 − 5/6 = 13/6 = 2 1/6
при a = 3 1/2: 1/2 + 5/12 = 6/12 + 5/12 = 11/12, 3 + 11/12 = 3 11/12 > 2 1/3 — нет 3 11/12 − 5/6 = 11/12 − 10/12 = 1/12, 3 + 1/12 = 3 1/12
при a = 3 3/4: 3/4 + 5/12 = 9/12 + 5/12 = 14/12 = 1 1/6, 3 + 7/6 = 4 1/6 > 2 1/3 — нет 4 1/6 − 5/6 = 25/6 − 5/6 = 20/6 = 3 1/3
при a = 3 7/8: 7/8 + 5/12 = 21/24 + 10/24 = 31/24, 3 + 31/24 = 4 7/24 > 2 1/3 — нет 4 7/24 − 5/6 = 103/24 − 20/24 = 83/24 = 3 11/24
при a = 4 1/12: 1/12 + 5/12 = 6/12 = 1/2, 4 + 1/2 = 4 1/2 > 2 1/3 — нет 4 1/2 − 5/6 = 27/6 − 10/6 = 17/6 = 2 5/6
при a = 4 5/8: 5/8 + 5/12 = 15/24 + 10/24 = 25/24, 4 + 25/24 = 5 1/24 > 2 1/3 — нет 5 1/24 − 5/6 = 25/24 − 20/24 = 5/24, 3 + 5/24 = 3 5/24
при a = 5 7/12: 7/12 + 5/12 = 12/12 = 1, 5 + 1 = 6 > 2 1/3 — нет 6 − 5/6 = 5 1/6
при a = 5 3/4: 3/4 + 5/12 = 9/12 + 5/12 = 14/12, 5 + 14/12 = 6 1/6 > 2 1/3 — нет 6 1/6 − 5/6 = 37/6 − 5/6 = 32/6 = 5 1/3