Tính: 28/15 . 1/4^2.3 + ( 8/15 - 69/60.5/23):51/54 A. 1/3 B. 20/13 C. 3 D. 13/20
Giải thích
Trả lời:
\[\frac{{28}}{{15}}.\frac{1}{{{4^2}}}.3 + \left( {\frac{8}{{15}} - \frac{{69}}{{60}}.\frac{5}{{23}}} \right):\frac{{51}}{{54}}\]
\[ = \frac{{28.1.3}}{{{{15.4}^2}}} + \left( {\frac{8}{{15}} - \frac{{23.3}}{{4.3.5}}.\frac{5}{{23}}} \right).\frac{{54}}{{51}}\]
\[ = \frac{{7.4.1.3}}{{3.5.4.4}} + \left( {\frac{8}{{15}} - \frac{1}{4}} \right).\frac{{54}}{{51}}\]
\[ = \frac{7}{{20}} + \left( {\frac{{32}}{{60}} - \frac{{15}}{{60}}} \right).\frac{{54}}{{51}}\]
\[ = \frac{7}{{20}} + \frac{{17}}{{60}}.\frac{{54}}{{51}}\]
\[ = \frac{7}{{20}} + \frac{{17}}{{6.10}}.\frac{{6.3.3}}{{17.3}}\]
\[ = \frac{7}{{20}} + \frac{3}{{10}}\]
\[ = \frac{7}{{20}} + \frac{6}{{20}}\]
\[ = \frac{{13}}{{20}}\]
Đáp án cần chọn là: D