N№4 После сокращения дробей приведите их к данному знаменателю: a) 15 20 = = 28 21 28 = = 36 б) 16 40 = = 45 28 36 = = 81 B) 48 72 = = 300 35 105 = = 6

Решение:

a) Давай разберем по порядку:

\[\frac{15}{20} = \frac{15 \div 5}{20 \div 5} = \frac{3}{4} = \frac{3 \times 7}{4 \times 7} = \frac{21}{28}\]

\[\frac{21}{28} = \frac{21 \div 7}{28 \div 7} = \frac{3}{4} = \frac{3 \times 9}{4 \times 9} = \frac{27}{36}\]

б) Давай разберем по порядку:

\[\frac{16}{40} = \frac{16 \div 8}{40 \div 8} = \frac{2}{5} = \frac{2 \times 9}{5 \times 9} = \frac{18}{45}\]

\[\frac{28}{36} = \frac{28 \div 4}{36 \div 4} = \frac{7}{9} = \frac{7 \times 9}{9 \times 9} = \frac{63}{81}\]

в) Давай разберем по порядку:

\[\frac{48}{72} = \frac{48 \div 24}{72 \div 24} = \frac{2}{3} = \frac{2 \times 100}{3 \times 100} = \frac{200}{300}\]

\[\frac{35}{105} = \frac{35 \div 35}{105 \div 35} = \frac{1}{3} = \frac{1 \times 2}{3 \times 2} = \frac{2}{6}\]

Ответ: a) \[\frac{21}{28}\], \[ \frac{27}{36}\]; б) \[ \frac{18}{45}\]; \[ \frac{63}{81}\]; в) \[ \frac{200}{300}\]; \[ \frac{2}{6}\]