Tính một cách hợp lí a. $8\dfrac{5}{7} 3,15 1\dfrac{2}{7} 4,35$ b. $\left(4\dfrac{5}{23}-2\dfrac{2}{5} 7\dfrac{7}{13}\right)-\left(3\dfrac{5}{23}-6\dfrac{6}{13}\right)$ c. \(-15\dfrac{1}{2}\tim...

1

CB

Cô Bé Họ Tạ

18 tháng 4 2018

a. $8 \frac{5}{7} + 3, 15 + 1 \frac{2}{7} + 4, 35$

$=$\dfrac{61}{7}+\dfrac{63}{20}+\dfrac{9}{7}+\dfrac{87}{20}$$

=$\left(\dfrac{61}{7}+\dfrac{9}{7}\right)+\left(\dfrac{63}{20}+\dfrac{87}{20}\right)$

=$10+\dfrac{15}{2}$

=$\dfrac{35}{2}$

b. $(4 \frac{5}{23} - 2 \frac{2}{5} + 7 \frac{7}{13}) - (3 \frac{5}{23} - 6 \frac{6}{13})$

$=$4\dfrac{5}{23}-2\dfrac{2}{5}+7\dfrac{7}{13}-3\dfrac{5}{23}+6\dfrac{6}{13}$$

=$\left(4\dfrac{5}{23}-3\dfrac{5}{23}\right)+\left(7\dfrac{7}{13}+6\dfrac{6}{13}\right)-2\dfrac{2}{5}$

=$1+14-\dfrac{12}{5}$

=15-$\dfrac{12}{5}$

=$\dfrac{63}{5}$

Câu C khó khó mình chưa giải được !!!

a)$\dfrac{-3}{7}+\dfrac{15}{26}-\left(\dfrac{2}{13}-\dfrac{3}{7}\right)$b)$2.\dfrac{3}{7}+\left(\dfrac{2}{9}-1\dfrac{3}{7}\right)-\dfrac{5}{3}:\dfrac{1}{9}$c)$\dfrac{-11}{23}.\dfrac{6}{7}+\dfrac{8}{7}.\dfrac{-11}{23}-\dfrac{1}{23}$d)$\left(\dfrac{377}{-231}-\dfrac{123}{89}+\dfrac{34}{791}\right).\left(\dfrac{1}{6}-\dfrac{1}{8}-\dfrac{1}{24}\right)$ nhanh lên giúp mình...

H

huongff2k3

23 tháng 7 2021

2

NL

Nguyễn Lê Phước Thịnh

23 tháng 7 2021

a) Ta có: $\dfrac{-3}{7}+\dfrac{15}{26}-\left(\dfrac{2}{13}-\dfrac{3}{7}\right)$

$=\dfrac{-3}{7}+\dfrac{15}{26}-\dfrac{2}{13}+\dfrac{3}{7}$

$=\dfrac{15}{26}-\dfrac{4}{26}$

$=\dfrac{11}{26}$

b) Ta có: $2\cdot\dfrac{3}{7}+\left(\dfrac{2}{9}-1\dfrac{3}{7}\right)-\dfrac{5}{3}:\dfrac{1}{9}$

$=\dfrac{6}{7}+\dfrac{2}{9}-\dfrac{10}{7}-\dfrac{5}{3}\cdot9$

$=\dfrac{-4}{7}+\dfrac{2}{9}-15$

$=\dfrac{-36}{63}+\dfrac{14}{63}-\dfrac{945}{63}$

$=\dfrac{-967}{63}$

c) Ta có: $\dfrac{-11}{23}\cdot\dfrac{6}{7}+\dfrac{8}{7}\cdot\dfrac{-11}{23}-\dfrac{1}{23}$

$=\dfrac{-11}{23}\cdot\left(\dfrac{6}{7}+\dfrac{8}{7}\right)-\dfrac{1}{23}$

$=\dfrac{-11}{23}\cdot2-\dfrac{1}{23}$

$=-1$

NL

Nguyễn Lê Phước Thịnh

23 tháng 7 2021

d) Ta có: $\left(\dfrac{377}{-231}-\dfrac{123}{89}+\dfrac{34}{791}\right)\cdot\left(\dfrac{1}{6}-\dfrac{1}{8}-\dfrac{1}{24}\right)$

$=\left(\dfrac{-377}{231}-\dfrac{123}{89}+\dfrac{34}{791}\right)\cdot\left(\dfrac{4}{24}-\dfrac{3}{24}-\dfrac{1}{24}\right)$

$=\left(\dfrac{-377}{231}-\dfrac{123}{89}+\dfrac{34}{791}\right)\cdot0$

=0

Bài 1.( 2 điểm)Tính bằng cách hợp...

F

fhdfhg

21 tháng 8 2021

1

NL

Nguyễn Lê Phước Thịnh

21 tháng 8 2021

1: $\dfrac{1}{2}+\dfrac{9}{10}+\dfrac{5}{6}-\dfrac{11}{14}-\dfrac{1}{3}+\dfrac{-4}{35}$

$=\left(\dfrac{1}{2}+\dfrac{5}{6}-\dfrac{1}{3}\right)+\dfrac{9}{10}-\left(\dfrac{11}{14}+\dfrac{4}{35}\right)$

$=\dfrac{3+5-2}{6}+\dfrac{9}{10}-\dfrac{55+8}{70}$

$=1+\dfrac{9}{10}-\dfrac{9}{10}$

=1

CH

Chử Hải Yến

29 tháng 5 2022

Tính hợp lý:

$A=\dfrac{7}{12}+\dfrac{5}{12}:6-\dfrac{11}{36}$ $B=\left(\dfrac{4}{5}+\dfrac{1}{2}\right):\left(\dfrac{3}{13}-\dfrac{8}{13}\right)$

$C=\left(\dfrac{2}{3}-\dfrac{1}{4}+\dfrac{5}{11}\right):\left(\dfrac{5}{12}+1-\dfrac{7}{11}\right)$

1

NL

Nguyễn Lê Phước Thịnh

29 tháng 5 2022

a: $A=\dfrac{7}{12}+\dfrac{5}{72}-\dfrac{11}{36}=\dfrac{42}{72}+\dfrac{5}{72}-\dfrac{22}{72}=\dfrac{25}{72}$

b: $B=\dfrac{8+5}{10}:\dfrac{-5}{13}=\dfrac{13}{10}\cdot\dfrac{13}{-5}=-\dfrac{169}{100}$

c: $C=\left(\dfrac{88}{132}-\dfrac{33}{132}+\dfrac{60}{132}\right):\left(\dfrac{55}{132}+\dfrac{132}{132}-\dfrac{84}{132}\right)$

$=\dfrac{88-33+60}{55+132-84}=\dfrac{115}{103}$

Đúng(2)

ZH

za hân

20 tháng 12 2021

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#Toán lớp 7

1

NL

Nguyễn Lê Phước Thịnh

20 tháng 12 2021

e: $=\dfrac{5^{30}\cdot3^{20}}{3^{15}\cdot5^{30}}=3^5=243$

Tính nhanh a) $\dfrac{-3}{7}+\dfrac{15}{26}-\left(\dfrac{2}{13}-\dfrac{3}{7}\right)$ b) $2.\dfrac{3}{7}+\left(\dfrac{2}{9}-1\dfrac{3}{7}\right)-\dfrac{5}{3}:\dfrac{1}{9}$ c) $\dfrac{-11}{23}.\dfrac{6}{7}+\dfrac{8}{7}.\dfrac{-11}{23}-\dfrac{1}{23}$ d)...

NN

Nkok_ Nhỏ_Dễ_Thươg

9 tháng 4 2017

2

HH

Huỳnh Huyền Linh

9 tháng 4 2017

a) $\dfrac{-3}{7}+\dfrac{15}{26}-\left(\dfrac{2}{13}-\dfrac{3}{7}\right)\\ =\dfrac{-3}{7}+\dfrac{15}{26}-\dfrac{2}{13}+\dfrac{3}{7}\\ =\left(\dfrac{-3}{7}+\dfrac{3}{7}\right)+\left(\dfrac{15}{26}-\dfrac{2}{13}\right)\\ =0+\left(\dfrac{15}{26}-\dfrac{4}{26}\right)\\ =0+\dfrac{11}{26}\\ =\dfrac{11}{26}$

NT

Nữ Thần Mặt Trăng

9 tháng 5 2017

$c)\dfrac{-11}{23}.\dfrac{6}{7}+\dfrac{8}{7}.\dfrac{-11}{23}-\dfrac{1}{23}\\=\dfrac{-1}{23}\left ( \dfrac{66}{7}+\dfrac{88}{7}+1 \right )\\ =\dfrac{-1}{23}.23=-1$

WT

Walker Trang

21 tháng 10 2017

Bài 2: tính a,...

#Toán lớp 7

1

TT

thám tử

21 tháng 10 2017

a. $\dfrac{11}{24}-\dfrac{5}{41}+\dfrac{13}{24}+0,5-\dfrac{36}{41}$

$=\left(\dfrac{11}{24}+\dfrac{13}{24}\right)+\left(\dfrac{-5}{41}-\dfrac{36}{41}\right)+0,5$

$=1+\left(-1\right)+0,5$

$=0,5$

b. $-12:\left(\dfrac{3}{4}-\dfrac{5}{6}\right)^2$

$=-12:\left(\dfrac{-1}{12}\right)^2$

$=-12:\dfrac{1}{144}$

$=-1728$

c. $\dfrac{7}{23}.\left[\left(-\dfrac{8}{6}\right)-\dfrac{45}{18}\right]$

$=\dfrac{7}{23}.\dfrac{-23}{6}$

$=\dfrac{-7}{6}$

d. $23\dfrac{1}{4}.\dfrac{7}{5}-13\dfrac{1}{4}:\dfrac{5}{7}$

$=23\dfrac{1}{4}.\dfrac{7}{5}-13\dfrac{1}{4}.\dfrac{7}{5}$

$=\left(23\dfrac{1}{4}-13\dfrac{1}{4}\right).\dfrac{7}{5}$

$=10.\dfrac{7}{5}$

$=14$

e. $\left(1+\dfrac{2}{3}-\dfrac{1}{4}\right).\left(0,8-\dfrac{3}{4}\right)^2$

$=\dfrac{17}{12}.\left(\dfrac{1}{20}\right)^2$

$=\dfrac{17}{12}.\dfrac{1}{400}=\dfrac{17}{4800}$

Tính a, 4$\times\left(-\dfrac{1}{2}\right)^3-2\times\left(-\dfrac{1}{2}\right)^2+3\times\left(-\dfrac{1}{2}\right)+1$ b, $\dfrac{4^6\times9^5+6^9\times120}{-8^4\times3^{12}+6^{11}}$ c, $\dfrac{155-\dfrac{10}{7}-\dfrac{5}{11}+\dfrac{5}{23}}{403-\dfrac{26}{7}-\dfrac{13}{11}+\dfrac{12}{23}}+\dfrac{\dfrac{3}{5}+\dfrac{3}{13}-0,9}{\dfrac{7}{91}+0,2-\dfrac{3}{10}}$ d,$\dfrac{30\times4^7\times3^{29}-5\times14^5\times2^{12}}{54\times6^{14}\times9^7-12\times8^5\times7^5}$ ...

TT

Trịnh Thị Thảo Nhi

26 tháng 7 2017

2

KL

Khánh Linh

26 tháng 7 2017

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

$=\left(-\dfrac{1}{2}\right)\left[\left(4\times-\dfrac{1}{2}\right)-\left(2\times-\dfrac{1}{2}\right)+3\right]+1$

$=\left(-\dfrac{1}{2}\right)\left(-2+1+3\right)+1$

$=\left(-\dfrac{1}{2}\right)2+1$

$=-1+1$

$=0$

@Trịnh Thị Thảo Nhi

C

chugialinh

29 tháng 4 2018

a, $4\times(-12)3-2\times(-12)2+3\times(-12)+14\times(-12)3-2\times(-12)2+3\times(-12)+1$

$=(-12)[(4\times-12)-(2\times-12)+3]+1=(-12)[(4\times-12)-(2\times-12)+3]+1$

$=(-12)(-2+1+3)+1=(-12)(-2+1+3)+1$

$=(-12)2+1=(-12)2+1$

$=-1+1=-1+1$

$=0=0$

SG

Sách Giáo Khoa

17 tháng 4 2017

Tính giá trị các biểu thức sau một cách hợp lí :

$A=\dfrac{7}{19}.\dfrac{8}{11}+\dfrac{7}{19}.\dfrac{3}{11}+\dfrac{12}{19}$

$B=\dfrac{5}{9}.\dfrac{7}{13}+\dfrac{5}{9}.\dfrac{9}{13}-\dfrac{5}{9}.\dfrac{3}{13}$

$C=\left(\dfrac{67}{111}+\dfrac{2}{33}-\dfrac{15}{117}\right).\left(\dfrac{1}{3}-\dfrac{1}{4}-\dfrac{1}{12}\right)$

2

BK

Bùi Khánh Thi

17 tháng 4 2017

$A= \frac{7}{19}.\left (\frac{8}{11}+\frac{3}{11} \right )+\frac{12}{19}=\frac{7}{19}.1 +\frac{12}{19}=1$

$B=\frac{5}{9}.\left (\frac{7}{13}+\frac{9}{13}-\frac{3}{13} \right )=\frac{5}{9}.\frac{7+9-3}{13}=\frac{5}{9}.\frac{13}{13}=\frac{5}{9}.$

$C=\left (\frac{67}{111}+\frac{2}{33}-\frac{15}{117} \right ).\left (\frac{1}{3}-\frac{1}{4}-\frac{1}{12} \right )$

$=\left (\frac{67}{111}+\frac{2}{33}-\frac{15}{117} \right ).\frac{4-3-1}{12}=\left (\frac{67}{111}+\frac{2}{33}-\frac{15}{117} \right ).0=0$

NT

nguyễn thị thúy

19 tháng 4 2017

Gợi ý: Sử dụng tính chất phân phối của phép nhân đối với phép cộng để nhóm thừa số chung ra ngoài.

Giải bài 76 trang 39 SGK Toán 6 Tập 2 | Giải toán lớp 6

Tính bằng cách hợp lí giá trị của biểu thức. A = $\left(3-\dfrac{1}{4} +\dfrac{3}{2}\right)$- $\left(5+\dfrac{1}{3}-\dfrac{5}{6}\right)$-$\left(6-\dfrac{7}{4}+\dfrac{3}{2}\right)$ B...

HP

Hồng Phong Đoàn

19 tháng 10 2023

#Toán lớp 7

2

NM

Nguyễn Minh Dương

VIP

19 tháng 10 2023

$A=\left(3-\dfrac{1}{4}+\dfrac{3}{2}\right)-\left(5+\dfrac{1}{3}-\dfrac{5}{6}\right)-\left(6-\dfrac{7}{4}+\dfrac{2}{3}\right)\\ \Rightarrow A=3-\dfrac{1}{4}+\dfrac{3}{2}-5-\dfrac{1}{3}+\dfrac{5}{6}-6+\dfrac{7}{4}-\dfrac{2}{3}\\ \Rightarrow A=\left(3-5-6\right)-\left(\dfrac{1}{4}+\dfrac{7}{4}\right)+\left(\dfrac{3}{2}+\dfrac{5}{6}-\dfrac{2}{3}\right)\\ \Rightarrow A=-8-\dfrac{3}{2}+\dfrac{5}{3}\\ =-\dfrac{47}{6}.\\ B=0,5+\dfrac{1}{3}+0,4+\dfrac{5}{7}+\dfrac{1}{6}-\dfrac{4}{35}+\dfrac{1}{41}$

$\Rightarrow B=\left(0,5+0,4\right)+\left(\dfrac{1}{3}+\dfrac{1}{6}\right)+\left(\dfrac{5}{7}-\dfrac{4}{35}\right)+\dfrac{1}{41}\\ \Rightarrow B=\dfrac{9}{10}+\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{1}{41}\\ \Rightarrow B=2+\dfrac{1}{41}\\ \Rightarrow B=\dfrac{83}{41}.$

Đúng(3)

NP

Ngô Phúc Nhã Uyên

VIP

29 tháng 10 2023

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