a)    \(\frac{3}{16}+\frac{4}{15}+\frac{5}{16}+\frac{1}{15}\)

\(=\left(\frac{3}{16}+\frac{5}{16}\right)+\left(\frac{4}{15}+\frac{1}{15}\right)\)

\(=\frac{1}{2}+\frac{1}{3}\)

\(=\frac{5}{6}\)

b)   \(\frac{6}{7}\times\frac{8}{15}\times\frac{7}{6}\times\frac{15}{16}\)

\(=\left(\frac{6}{7}\times\frac{7}{6}\right)\times\left(\frac{8}{15}\times\frac{15}{16}\right)\)

\(=1\times\frac{1}{2}=\frac{1}{2}\)

c)   \(\frac{19}{20}\times\frac{13}{21}+\frac{9}{20}\times\frac{8}{21}\)

\(=\frac{19\times13}{20\times21}+\frac{9\times8}{20\times21}\)

\(=\frac{247}{420}+\frac{72}{420}\)

\(=\frac{319}{420}\)

còn phần D đâu bn 

tích cho chị nha

 câu a)     = 5/6

 câu b = 1/2

 câu c = 319/420

Phương pháp giải:

Trừ nhẩm các số rồi điền kết quả vào chỗ trống.

Lời giải chi tiết:

a)

15 − 6 = 9         15 − 7 = 8

15 − 8 = 7         15 − 9 = 6

16 − 7 = 9         16 − 8 = 8

16 − 9 = 7         17 − 8 = 9

17 − 9 = 8         18 − 9 = 9

b)

18 − 8 − 1 = 9       18 − 9 = 9

15 − 5 − 2 = 8       15 − 7 = 8

16 − 6 − 3 = 7       16 − 9 = 7

15 - 6 = 9, 

15 - 8 =7, 

15 - 7 = 8, 

15 - 9 = 6

Tính nhẩm rồi điền kết quả vào chỗ trống.

14 - 1 = 13     15 - 4 = 11     17 - 2 = 15     15 - 3 = 12

15 - 1 = 14     19 - 8 = 11     16 - 2 = 14     15 - 2 = 13

\(a,\dfrac{1}{2}+\left(-\dfrac{3}{4}\right)=\dfrac{2}{4}+\left(-\dfrac{3}{4}\right)=-\dfrac{1}{4}\)

\(b,\dfrac{2}{5}+\left(-\dfrac{1}{16}\right)+\left(-\dfrac{9}{5}\right)+\left(-\dfrac{5}{16}\right)=\left(\dfrac{2}{5}-\dfrac{9}{5}\right)-\left(\dfrac{1}{16}+\dfrac{5}{16}\right)=\dfrac{-7}{5}-1=\dfrac{-12}{5}\)

\(c,\dfrac{-2}{13}+\dfrac{8}{15}+\dfrac{10}{20}+\dfrac{15}{13}+\left(-\dfrac{23}{15}\right)=\left(\dfrac{-2}{13}+\dfrac{15}{13}\right)+\left(\dfrac{8}{15}+\dfrac{-23}{15}\right)+\dfrac{1}{2}=1+\left(-1\right)+\dfrac{1}{2}=\dfrac{1}{2}\)

(Cho mik làm lại nha)

\(a,\dfrac{1}{2}+\left(-\dfrac{3}{4}\right)=\dfrac{2}{4}+\left(-\dfrac{3}{4}\right)=-\dfrac{1}{4}\)

\(a,\dfrac{2}{5}+\left(-\dfrac{1}{16}\right)+\left(-\dfrac{9}{5}\right)+\left(-\dfrac{5}{16}\right)=\left(\dfrac{2}{5}+\dfrac{-9}{5}\right)-\left(\dfrac{1}{16}+\dfrac{5}{16}\right)=\dfrac{-7}{5}-\dfrac{6}{16}=\dfrac{-71}{40}\)

\(c,\dfrac{-2}{13}+\dfrac{8}{15}+\dfrac{10}{20}+\dfrac{15}{13}+\left(-\dfrac{23}{15}\right)=\left(\dfrac{-2}{13}+\dfrac{15}{13}\right)+\left(\dfrac{8}{15}+\dfrac{-23}{15}\right)+\dfrac{1}{2}=1+\left(-1\right)+\dfrac{1}{2}=\dfrac{1}{2}\)

Bài này dễ:=\(\frac{3}{5}\)x    \(\frac{1}{\frac{-1}{15}-\frac{1}{6}}\)+\(\frac{3}{5}\)x   \(\frac{1}{\frac{-1}{3}-\frac{16}{15}}\).Tự giải tiếp nhé,nhớ chọn cho Long đẹp trai này nhé!

           \(\frac{31}{25}\) + ( \(\frac{15}{16}\) - \(\frac{6}{15}\) ) + \(\frac{1}{16}\)

           = \(\frac{31}{25}\) + \(\frac{43}{80}\) + \(\frac{1}{16}\)

           = \(\frac{711}{400}\) + \(\frac{1}{16}\) 

           = \(\frac{46}{25}\)

\(\frac{31}{25}+\left(\frac{15}{16}-\frac{6}{15}\right)+\frac{1}{16}=\frac{31}{25}+\frac{15}{16}-\frac{6}{15}+\frac{1}{16}\) 

\(\frac{31}{25}-\frac{6}{15}+1=\frac{31}{25}-\frac{10}{25}+\frac{25}{25}=\frac{46}{25}\)

   31/25 + ( 15/16 - 6/15 ) + 1/16

= 31/25 + 15/16 - 6/15 + 1/16

= ( 31/25 - 6/15 ) + ( 15/16+ 1/16 )

= 21/5 + 1

= 46/25

Chú ý : / này là phần nha

= 

12 + 3 - 1 = 14     17 - 5 + 2 = 14     15 - 3 - 1 = 11

15 + 2 - 1 = 16     16 - 2 + 1 = 15     19 - 2 - 5 = 12

    ( 1- \(\dfrac{1}{15}\))x ( 1 - \(\dfrac{1}{16}\))x(1- \(\dfrac{1}{17}\)) x.....x(1- \(\dfrac{1}{100}\))

=  \(\dfrac{14}{15}\) x \(\dfrac{15}{16}\)x \(\dfrac{16}{17}\)x......x\(\dfrac{99}{100}\)

= \(\dfrac{15\times16\times17\times.....\times99}{15\times16\times17\times.....\times99}\) x \(\dfrac{14}{100}\)

=  1 x \(\dfrac{14}{100}\)

= \(\dfrac{7}{50}\)