Question

579номер надо толька номер 4)
А 580 2) и 4)

Answer 1

№579 (4)
1)
$frac{10}{13} times frac{11}{12} = frac{10 times 11}{13 times 12} = frac{110}{156} = frac{55 times 2}{78 times 2} = frac{55}{78}$
2)
$frac{12}{55} times frac{13}{20} = frac{12 times 13}{55 times 20} = frac{156}{1100} = frac{39 times 4}{275 times 4} = frac{39}{275}$
3)
$frac{55}{78} times frac{39}{275} = frac{2145}{21450} = frac{1}{10}$
Ответ:
$frac{1}{10}$
№580 (2)
1)
$frac{4}{9} times frac{3}{4} + frac{2}{3}$
2)
$frac{4}{9} times frac{3}{4} = frac{4 times 3}{9 times 4} = frac{12}{36} = frac{1}{3}$
3)
$frac{1}{3} + frac{2}{3} = frac{1 + 2}{3} = frac{3}{3} = 1$
№580 (4)
1)
$2 frac{3}{10} times 2 frac{1}{2} + frac{1}{2}$
2)
$2 frac{2}{10} times 2 frac{1}{2} = frac{3 + 2 times 10}{10} times frac{1 + 2 times 2}{2} = frac{23}{10} times frac{5}{2} = frac{23 times 5}{10 times 2} = frac{115}{20} = frac{23 times 5}{4 times 5} = frac{23}{4} = frac{3 + 5 times 4}{4} = 5 frac{3}{4}$
3)
$5 frac{3}{4} + frac{1}{2} = 5 + frac{3}{4} + frac{1}{2} = 5 + frac{3 times 1}{4 times 1} + frac{1 times 2}{2 times 2} = 5 + frac{3}{4} + frac{2}{4} = 5 + frac{3 + 2}{4} = 5 frac{5}{4} = 5 frac{1 + 1 times 4}{4} = 6 frac{1}{4}$