Question

[do thi anh]

Tính nhanh

a:41/25+17/100)+39/25                               b:17/9+19/13+14/16+7/13+10/6+1/9

c:2/3*13/4*3/2*7/3*4/7                                   d:21/2*7/5*7/5*79/2

e:1/1*2+1/2*3+1/3*4+1/4*5                            g:1/12+1/20+1/30+1/42

Giúp mình với mình cần gấp lắm

Answer 1

[Nguyễn Thị Thương Hoài]

c \(\dfrac{2}{3}\times\dfrac{13}{4}\times\dfrac{3}{2}\times\dfrac{7}{3}\times\dfrac{4}{7}\)

= \(\dfrac{2\times13\times3\times7\times4}{3\times4\times2\times3\times7}\)

= \(\dfrac{13}{3}\)

\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}\)

=\(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}\)

=\(\dfrac{1}{1}-\dfrac{1}{5}\)

=\(\dfrac{4}{5}\)

Answer 2

[Nguyễn Thị Thương Hoài]

a, (\(\dfrac{41}{25}\) + \(\dfrac{17}{100}\)) + \(\dfrac{39}{25}\)

= (\(\dfrac{41}{25}\) + \(\dfrac{39}{25}\)) + \(\dfrac{17}{100}\) 

= \(\dfrac{80}{25}\) + \(\dfrac{17}{100}\)

= \(\dfrac{320}{100}\) + \(\dfrac{17}{100}\)

= \(\dfrac{337}{100}\)

g, \(\dfrac{1}{12}\) + \(\dfrac{1}{20}\) + \(\dfrac{1}{30}\) + \(\dfrac{1}{42}\)

= \(\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}\)

= \(\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)

= \(\dfrac{1}{3}-\dfrac{1}{7}\)

= \(\dfrac{7}{21}-\dfrac{3}{21}\)

= \(\dfrac{4}{21}\)