Tính:

a) \(\frac{1}{3} + \frac{5}{2} - \frac{1}{4}\)	= …………………	b)\(\frac{1}{2} \times \frac{5}{7}:\frac{1}{3}\)	= …………………
	= …………………		= …………………

Lời giải

Lời giải

a) \(\left( {\frac{5}{7} \times \frac{3}{7}} \right) + \frac{1}{2} = \frac{{15}}{{49}} + \frac{1}{2} = \frac{{30}}{{98}} + \frac{{49}}{{98}} = \frac{{79}}{{98}}\)

b) \(\frac{5}{4} \times \frac{2}{3} - \frac{5}{4} \times \frac{1}{9} = \frac{5}{4} \times \left( {\frac{2}{3} - \frac{1}{9}} \right) = \frac{5}{4} \times \left( {\frac{6}{9} - \frac{1}{9}} \right) = \frac{5}{4} \times \frac{5}{9} = \frac{{25}}{{36}}\)

c) \(\frac{{3 \times 8 \times 4 \times 5}}{{3 \times 7 \times 6 \times 5}} = \frac{{\bcancel{3} \times 4 \times \bcancel{2} \times 4 \times \bcancel{5}}}{{\bcancel{3} \times 7 \times \bcancel{2} \times 3 \times \bcancel{5}}} = \frac{{16}}{{21}}\)

d) \(\left( {\frac{5}{4} - \frac{2}{3}} \right):\frac{4}{7} = \left( {\frac{{15}}{{12}} - \frac{8}{{12}}} \right) \times \frac{7}{4} = \frac{7}{{12}} \times \frac{7}{4} = \frac{{49}}{{48}}\)