Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
bài 3 :
Số học sinh trung bình là :
\(1200\times\dfrac{5}{8}=750\) ( hs)
Số học sinh khá là :
\(750\times\dfrac{2}{5}=300\) (hs)
Số học sinh giỏi là :
\(1200-750-300=150\left(hs\right)\)
b) So với cả trường chứ ?
3b ) Tỉ số của hs giỏi so với toàn trường :150: 1200 = 0,125
Tỉ số phần trăm của hs giỏi so vs toàn trường là : 12,5%
\(4\dfrac{1}{3}.\dfrac{4}{9}+13\dfrac{2}{3}.\dfrac{4}{9}\)\(=\dfrac{4}{9}\left(4\dfrac{1}{3}+13\dfrac{2}{3}\right)=\dfrac{4}{9}.18=8\)
\(5\dfrac{1}{4}.\dfrac{3}{8}+10\dfrac{3}{4}.\dfrac{3}{8}=\dfrac{3}{8}\left(5\dfrac{1}{4}+10\dfrac{3}{4}\right)=\dfrac{3}{8}.16=6\)
a) \(\left(\dfrac{-3}{4}+\dfrac{2}{5}\right):\dfrac{3}{7}+\left(\dfrac{3}{5}+\dfrac{-9}{4}\right):\dfrac{3}{7}\)
\(=\left(\dfrac{-3}{4}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{-9}{4}\right):\dfrac{3}{7}\)
\(=-2:\dfrac{3}{7}=\dfrac{-14}{3}\)
\(\dfrac{7}{8}:\left(\dfrac{2}{9}-\dfrac{1}{18}\right)+\dfrac{7}{8}:\left(\dfrac{1}{36}-\dfrac{5}{12}\right)\)
\(=\dfrac{7}{8}:\dfrac{1}{6}+\dfrac{7}{8}:\dfrac{-7}{18}\)
\(=\dfrac{7}{8}:\left(\dfrac{1}{6}+\dfrac{-7}{18}\right)=\dfrac{7}{8}:\dfrac{-2}{9}=\dfrac{63}{-16}\)
3/ Chu vi hình chữ nhật:
\(\left(\dfrac{1}{4}+\dfrac{3}{10}\right)\cdot2=\dfrac{11}{10}\) (chưa biết đơn vị)
Diện tích hình chữ nhật:
\(\dfrac{1}{4}\cdot\dfrac{3}{10}=\dfrac{11}{20}\) (chưa biết đơn vị)
\(A=\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{11}+1\dfrac{5}{7}\)
\(=\dfrac{-5}{7}\left(\dfrac{2}{11}+\dfrac{9}{11}\right)+1+\dfrac{-5}{7}\)
\(=\dfrac{-5}{7}+\dfrac{-5}{7}+1=\dfrac{-3}{7}\)
\(B=0,7.2\dfrac{2}{3}.20.0,375.\dfrac{5}{28}\)
\(=\dfrac{7}{10}.\dfrac{8}{3}.20.\dfrac{3}{8}.\dfrac{5}{28}\)
\(=\dfrac{7}{10}.\dfrac{5}{28}.20=\dfrac{5}{2}.\)
Ta có :
A = \(\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{11}+1\dfrac{5}{7}\)
= \(\dfrac{5}{7}.\dfrac{-2}{11}-\dfrac{5}{7}.\dfrac{9}{11}+\dfrac{5}{7}+1\)
= \(\left(\dfrac{5}{7}.\dfrac{-2}{11}-\dfrac{5}{7}.\dfrac{9}{11}+\dfrac{5}{7}\right)+1\)
= \(\dfrac{5}{7}.\left(\dfrac{-2}{11}-\dfrac{9}{11}+1\right)+1\)
= \(\dfrac{5}{7}.0+1\)
= 1
B = \(0,7.2\dfrac{2}{3}.20.0,375.\dfrac{5}{28}\)
= \(\dfrac{7}{10}.\dfrac{8}{3}.20.\dfrac{3}{8}.\dfrac{5}{28}\)
= \(\left(\dfrac{7}{10}.20\right).\left(\dfrac{8}{3}.\dfrac{3}{8}\right).\dfrac{5}{28}\)
= 14.1.\(\dfrac{5}{28}\)
= \(\dfrac{5}{2}\)
Vậy A = 1
B = \(\dfrac{5}{2}\)
a) \(\dfrac{1}{6},\dfrac{1}{3},\dfrac{1}{2},\dfrac{2}{3}\)
Vì \(\dfrac{1}{6}:\dfrac{1}{2}=\dfrac{1}{3}\) ; \(\dfrac{1}{3}:\dfrac{2}{3}=\dfrac{1}{2}\) nên suy ra \(\dfrac{1}{2}:\dfrac{3}{4}=\dfrac{2}{3}\)
Vậy số để điền vào chỗ trống là \(\dfrac{2}{3}\).
b) \(\dfrac{1}{8},\dfrac{5}{24},\dfrac{7}{24},\dfrac{3}{8}\)
Vì \(\dfrac{1}{8}:\dfrac{3}{5}=\dfrac{5}{24}\) ; \(\dfrac{5}{24}:\dfrac{5}{7}=\dfrac{7}{24}\) nên suy ra \(\dfrac{7}{24}:\dfrac{7}{9}=\dfrac{3}{8}\)
Vậy số để điền vào chỗ trống là \(\dfrac{3}{8}\).
c) \(\dfrac{1}{5},\dfrac{1}{4},\dfrac{3}{10},\dfrac{7}{20}\)
Vì \(\dfrac{1}{5}:\dfrac{4}{5}=\dfrac{1}{4}\) ; \(\dfrac{1}{4}:\dfrac{5}{6}=\dfrac{3}{10}\) nên suy ra \(\dfrac{3}{10}:\dfrac{6}{7}=\dfrac{7}{20}\)
Vậy số để điền vào chỗ trống là \(\dfrac{7}{20}\).
Trời ơi cái đề bài !!!
Thoy thì làm từng câu vậy
a) \(I=10101.\left(\dfrac{5}{111111}+\dfrac{5}{222222}-\dfrac{4}{111111}\right)\)
\(I=10101.\left(\dfrac{10}{222222}+\dfrac{5}{222222}-\dfrac{8}{222222}\right)\)
\(I=10101.\left(\dfrac{15}{222222}-\dfrac{8}{222222}\right)\)
\(I=10101.\dfrac{7}{222222}\)
\(I=\dfrac{7}{22}\)
\(\dfrac{3}{8}+\dfrac{5}{8}=\dfrac{3+5}{8}=\dfrac{8}{8}=1\)
\(\dfrac{-1}{2}+\dfrac{5}{7}=\dfrac{-7}{14}+\dfrac{10}{14}=\dfrac{\left(-7\right)+10}{14}=\dfrac{3}{14}\)
\(\dfrac{9}{11}\cdot\dfrac{5}{8}=\dfrac{9\cdot5}{11\cdot8}=\dfrac{45}{88}\)
\(\dfrac{3}{4}:\dfrac{4}{3}=\dfrac{3}{4}\cdot\dfrac{3}{4}=\dfrac{3\cdot3}{4\cdot4}=\dfrac{9}{16}\)
\(\dfrac{7}{3}=2\dfrac{1}{3}\)
\(4\dfrac{3}{7}\)
\(1\dfrac{3}{4}+3\dfrac{5}{9}\\ =1\dfrac{27}{36}+3\dfrac{20}{36}\\ =4\dfrac{47}{36}\\ =5\dfrac{11}{36}\)
\(1\dfrac{5}{4}-2\dfrac{7}{4}\\ =2\dfrac{1}{4}-2\dfrac{7}{4}\\ =\dfrac{-6}{4}\\ =\dfrac{-3}{2}\)