Question

Вычислить.
1)-2 1/4 + 1,7
2)1 1/3-3,3
3)0,48 : (-12/13)

Answer 1

$1) \, -2 \cfrac{1}{4} + 1.7 = -\cfrac{9}{4} + 1 \cfrac{7}{10} = -\cfrac{9}{4} + \cfrac{17}{10}= \cfrac{-9\cdot5+17\cdot2}{20}= \\\\ = \cfrac{-45+34}{20}= \cfrac{-11}{20}=-0.55.$

$2) \, 1 \cfrac{1}{3} -3.3=1\cfrac{1}{3}-3\cfrac{3}{10}=\cfrac{4}{3}-\cfrac{33}{10}= \cfrac{4\cdot10 - 33\cdot 3}{30}=\cfrac{40-99}{30}= \\\\ =\cfrac{-59}{30}=-1\cfrac{29}{30}.$

$3) \, 0.48 : \left(-\cfrac{12}{13}\right)= \cfrac{48}{100} : \left(-\cfrac{12}{13}\right) = \cfrac{12}{25} \cdot \left(-\cfrac{13}{12}\right) = - \cfrac{12\cdot13}{25\cdot12} = \\\\ = -\cfrac{13}{25} = -0.52.$