b) Minh thu gom được \(\frac{3}{2}\) kg giấy vụn. Lan thu được ít hơn Minh \[\frac{1}{4}\] kg giấy vụn. Đức thu gom được nhiều hơn Lan \(\frac{3}{4}\) kg giấy vụn. Vậy cả ba bạn thu gom được số ki – lô – gam giấy vụn là:

a) \(\frac{9}{5}\,\, + \,\,\frac{1}{2} = \frac{{18}}{{10}} + \frac{5}{{10}} = \frac{{23}}{{10}}\)

b) \(\frac{8}{7}\,\, \times \,\,\frac{{21}}{4} = \frac{{168}}{{28}} = 6\)

c) \(\frac{{11}}{3}\,\, + \,\,\frac{6}{7}\,\, + \,\,\frac{4}{3} = \frac{{77}}{{21}} + \frac{{18}}{{21}} + \frac{{28}}{{21}} = \frac{{123}}{{21}}\)\(\)

d) \(\frac{{17}}{3}\,\, - \,\,\frac{4}{5} = \frac{{85}}{{15}} - \frac{{12}}{{15}} = \frac{{73}}{{15}}\)

e) \(\frac{{45}}{{16}}\,\,:\,\,\frac{9}{8} = \frac{{45}}{{16}} \times \frac{8}{9} = \frac{{360}}{{144}} = \frac{5}{2}\)

f) \(\frac{9}{{10}}\,\, \times \,\,\frac{5}{6}\,\,:\,\,3 = \frac{9}{{10}} \times \frac{5}{6} \times \frac{1}{3} = \frac{{45}}{{180}} = \frac{1}{4}\)