Question

4. Calculati: a)2 1/12-3/8-1 5/16;b)4 5/21-7/12-2 3/4;c)3 1/9-5/18-1 5/24.​

Answer 1

Răspuns:

Explicație pas cu pas:

a)2 1/12-3/8-1 5/16;

$2\frac{1}{12} -\frac{3}{8} -1\frac{5}{16} =\\\frac{2*12+1}{12} -\frac{3}{8} -\frac{1*16+5}{16} =\\\\\frac{25}{12} -\frac{3}{8} -\frac{21}{16} =\\(Aducem -la - acelasi- numitor)\\\frac{25*4}{12*4} -\frac{3*6}{8*6} -\frac{21*3}{16*3} =\\\\\frac{100}{48} -\frac{18}{48} -\frac{63}{48} =\\\\\frac{100-18+63}{48} =\frac{145}{48}=\frac{145}{48}$

b)

$4\frac{5}{21} - \frac{7}{12}- 2\frac{3}{4}\\\\\frac{4*21+5}{21} - \frac{7}{12}- \frac{2*4+3}{4}\\\\\\\frac{84+5}{21} - \frac{7}{12}- \frac{8+3}{4}\\\\\\\frac{89}{21} - \frac{7}{12}- \frac{11}{4}\\\\\\\frac{89*4}{21*4} - \frac{7*7}{12*7}- \frac{11*21}{4*21}\\\\\\\frac{356}{84} - \frac{49}{84}- \frac{231}{84}\\\\\\\frac{356-49-231}{84} \\\\\\\frac{356-49-231}{84}= \frac{76}{84}= \frac{19}{21}$;