Bài tập: Hỗn số. Số thập phân. Phần trăm chọn lọc, có đáp án

Đáp án là D

Ta có 4:3 bằng 1 (dư 1 ) nên

Đáp án là B

Ta có:

Đáp án là A

Ta có: 131/1000 = 0,131

Đáp án là A

Ta có: 0,25 = 25/100

0,25 = 25/100 = 1/4

Đáp án là B

Ta có: 47/100 = 47%

Đáp án là C

Đáp án là B

Đáp án là D

Đáp án là C

Đáp án là A

Đáp án A

$4x+5\frac{1}{5}x=\frac{27}{25}$

 $$\begin{gathered} x\left(4+5\frac{1}{5}\right)=\frac{27}{25} \\ x.\frac{46}{5}=\frac{27}{25} \\ x=\frac{27}{25}:\frac{46}{5} \\ x= \frac{27}{25}.\frac{5}{46} \\ x = \frac{27}{230} \end{gathered}$$

Vậy $x = \frac{27}{230}$

Đáp án C

Đáp án A:  $\left(-3\frac{3}{4}\right).1\frac{1}{2}=-\frac{15}{4}.\frac{3}{2}=-\frac{45}{8}=-5\frac{5}{8}\not\equiv -3\frac{3}{8}$  nên A sai.

Đáp án B:  $3\frac{3}{4}:1\frac{1}{5}=\frac{15}{4}:\frac{6}{5}=\frac{15}{4}.\frac{5}{6}=\frac{25}{8}=3\frac{1}{8}\not\equiv 3\frac{3}{20}$  nên B sai.

Đáp án C:  $\left(-3\right)-\left(-2\frac{2}{5}\right)=\left(-3\right)-\left(-\frac{12}{5}\right)=\left(-3\right)+\frac{12}{5}=\frac{-3}{5}$  nên C đúng.

Đáp án D: $5\frac{7}{10}.15=\frac{57}{10}.15=\frac{171}{2}\not\equiv \frac{105}{2}$ nên D sai.

Đáp án D 

Đáp án A:  $3\frac{1}{4}.2\frac{6}{13}=\frac{13}{4}.\frac{32}{13}=8$  nên A đúng

Đáp án B: $5\frac{1}{3}:2\frac{2}{9}=\frac{16}{3}:\frac{20}{9}=\frac{16}{3}.\frac{9}{20}=\frac{12}{5}=2\frac{2}{5}$  nên B đúng

Đáp án C: $\left(-3\right).\left(6\frac{1}{7}\right)=\left(-3\right).\frac{43}{7}=-\frac{129}{7}=-18\frac{3}{7}$  nên C đúng.

Đáp án D: $10\frac{8}{9}:2=\frac{98}{9}.\frac{1}{2}=\frac{49}{9}=5\frac{4}{9}\ne 5\frac{8}{9}$  nên D sai.

Đáp án B

$$\begin{gathered} A=\left(4\frac{5}{17}-3\frac{4}{5}+8\frac{15}{29}\right)-\left(3\frac{5}{17}-6\frac{14}{29}\right) \\ A=4\frac{5}{17}-3\frac{4}{5}+8\frac{15}{29}-3\frac{5}{17}+6\frac{14}{29} \\ A=\left(4\frac{5}{17}-3\frac{5}{17}\right)+\left(8\frac{15}{29}+6\frac{14}{29}\right)-3\frac{4}{5} \\ A=\left(4-3\right)+\left(\frac{5}{17}-\frac{5}{17}\right)+\left(8+6\right)+\left(\frac{15}{29}+\frac{14}{29}\right)-3\frac{4}{5} \\ A= 1+0+14+1-3\frac{4}{5} \\ A= 16-3\frac{4}{5} \\ A= 15\frac{5}{5}-3\frac{4}{5}=12\frac{1}{5} \end{gathered}$$

Đáp án B

$$\begin{gathered} A=\left(17\frac{29}{31}-3\frac{7}{8}+17\frac{51}{59}\right)-\left(2\frac{29}{31}+7\frac{51}{59}-4\right) \\ =17\frac{29}{31}-3\frac{7}{8}+17\frac{51}{59}-2\frac{29}{31}-7\frac{51}{59}+4 \\ =\left(17\frac{29}{31}-2\frac{29}{31}\right)-\left(17\frac{51}{59}-7\frac{51}{59}+4\right) \\ =15+10-\frac{31}{8}+4=\frac{201}{4}=25\frac{1}{8} \end{gathered}$$

Đáp án A

$$\begin{gathered} M=60\frac{7}{13}x+50\frac{8}{13}.x-11\frac{2}{13}.x \\ M=\left(60\frac{7}{13}+50\frac{8}{13}-11\frac{2}{13}\right).x \\ M=\left[\left(60+50-11\right)+\left(\frac{7}{13}+\frac{8}{13}-\frac{2}{13}\right)\right].x \\ M=\left(99+1\right).x=100x \end{gathered}$$

Thay $x=-8\frac{7}{10}$ vào M ta được:

$M=100.\left(-8\frac{7}{10}\right)$=$100.\left(-\frac{87}{10}\right)=-870$

Đáp án A

Đáp án B

$$\begin{gathered} N=-\frac{1}{7}\left(9\frac{1}{2}-8,75\right):\frac{2}{7}+0,625:1\frac{2}{3} \\ =-\frac{1}{7}\left(\frac{19}{2}-\frac{35}{4}\right).\frac{7}{2}+\frac{5}{8}:\frac{5}{3} \\ =-\frac{1}{7}.\frac{3}{4}.\frac{7}{2}+\frac{5}{8}.\frac{3}{5} \\ =-\frac{3}{8}+\frac{3}{8}=0 \end{gathered}$$

Đáp án B

$$\begin{gathered} A=\frac{1,6:\left(1{\displaystyle \frac{3}{5}}.1,25\right)}{0,64-{\displaystyle \frac{1}{25}}}+\frac{\left(1,08-{\displaystyle \frac{2}{25}}\right):{\displaystyle \frac{4}{7}}}{\left(5{\displaystyle \frac{5}{9}}-2{\displaystyle \frac{1}{4}}\right).2{\displaystyle \frac{2}{17}}}+0,6+0,5:\frac{2}{5} \\ =\frac{{\displaystyle \frac{8}{5}}:\left({\displaystyle \frac{8}{5}}.{\displaystyle \frac{5}{4}}\right)}{{\displaystyle \frac{16}{25}}-{\displaystyle \frac{1}{25}}}+\frac{\left({\displaystyle \frac{27}{25}}-{\displaystyle \frac{2}{25}}\right):{\displaystyle \frac{4}{7}}}{\left({\displaystyle \frac{50}{9}}-{\displaystyle \frac{9}{4}}\right).{\displaystyle \frac{36}{17}}}+\frac{3}{5}.\frac{1}{2}:\frac{2}{5} \\ =\frac{{\displaystyle \frac{4}{5}}}{{\displaystyle \frac{3}{5}}}+\frac{{\displaystyle \frac{7}{4}}}{7}+\frac{3}{5}.\frac{1}{2}:\frac{2}{5} \\ =\frac{4}{3}+\frac{1}{4}+\frac{3}{5}.\frac{1}{2}:\frac{2}{5} \\ =\frac{4}{3}+\frac{1}{4}+\frac{3}{5}.\frac{1}{2}.\frac{5}{2} \\ =\frac{7}{3} \end{gathered}$$

Đáp án C

$$\begin{gathered} \frac{\left(1,16-x\right).5,25}{\left(10{\displaystyle \frac{5}{9}}-7{\displaystyle \frac{1}{4}}\right).2{\displaystyle \frac{2}{17}}}=75\% \\ \iff \frac{\left({\displaystyle \frac{29}{25}}-x\right).{\displaystyle \frac{21}{4}}}{\left({\displaystyle \frac{95}{9}}-{\displaystyle \frac{29}{4}}\right).{\displaystyle \frac{36}{17}}}=\frac{3}{4} \\ \iff \frac{\left({\displaystyle \frac{29}{25}-x}\right).{\displaystyle \frac{21}{4}}}{{\displaystyle \frac{119}{36}}.{\displaystyle \frac{36}{17}}}=\frac{3}{4} \\ \iff \frac{\left({\displaystyle \frac{29}{25}-x}\right).{\displaystyle \frac{21}{4}}}{{\displaystyle 7}}=\frac{3}{4} \\ \iff \left(\frac{29}{25}-x\right).\frac{21}{4}=\frac{21}{4} \\ \iff \frac{29}{25}-x=1 \\ \iff x = \frac{4}{25} \end{gathered}$$

Đáp án B

$$\begin{gathered} 8\frac{1}{5}.x.\left(11\frac{94}{1591}-6\frac{38}{1517}\right):8\frac{11}{43}=75\% \\ \iff \frac{41}{5}.x.\left[\left(11-6\right)+\left(\frac{94}{1591}-\frac{38}{1517}\right)\right].\frac{355}{43}=\frac{3}{4} \\ \iff \frac{41}{5}.x.\frac{8875}{1763}.\frac{43}{355}=\frac{3}{4} \\ \iff 5.x=\frac{3}{4} \\ \iff x=\frac{3}{20} \end{gathered}$$

Đáp án A

$$\begin{gathered} 6\frac{1}{3}:4\frac{2}{9}<x<\left(10\frac{2}{9}+2\frac{2}{5}\right)-6\frac{2}{9} \\ \frac{19}{3}:\frac{38}{9}<x<\frac{92}{9}+\frac{12}{5}-\frac{56}{9} \\ \frac{3}{2}<x<\frac{32}{5} \end{gathered}$$

Ta có :

$$\begin{gathered} \frac{3}{2}<x<\frac{32}{5} \\ 1,5<x<6,4 \end{gathered}$$

Vì x là số tự nhiên nên x∈{2;3;4;5;6}

Đáp án C 

$$\begin{gathered} 2y+30\%y=-2,3 \\ 2y+\frac{3}{10}y=-2,3 \\ \frac{23}{10}y=-\frac{23}{10} \\ y=-\frac{23}{10}:\frac{23}{10} \\ y=-1 \end{gathered}$$