Bài 1:

Chiều cao của tam giác là:

12,56 x 2 : 8 = 3,14 (cm)

Đáp số: 3,14 cm

Bài 2:

a) 2 + 5/7 = 2/1 + 5/7 = 14/7 + 5/7 = 19/7

b) 13/5 - 2 = 13/5 - 2/1 = 13/5 - 10/5 = 3/5

c) 1/8 + 3/4 - 1/6 = 3/24 + 18/24 - 6/24 = 17/24

e) 12/5 - 2/2 + 7/7 - 6/6 = 12/5 - 1 + 1 - 1 = 12/5 - 1 = 12/5 - 5/5 = 7/5

Bài 3:

A = 55/11.16 + 55/16.21 + 55/21.26 + 55/26.31 + 55/31.36 + 55/36.41

A = 11.(1/11 - 1/16 + 1/16 - 1/21 + 1/21 - 1/26 + 1/26 - 1/31 + 1/31 - 1/36 + 1/36 - 1/41)

A = 11.(1/11 - 1/41)

A = 11.30/451

A = 30/41

Bài 1 :

Chiều cao tam giác đó là :

\(12,56.2:8=3,14\) ( cm )

Vậy : chiều cao tam giác đó là \(3,14\) cm.

Bài 2 :

a) \(2+\frac{5}{7}=\frac{14}{7}+\frac{5}{7}=\frac{19}{7}\)

b) \(\frac{13}{15}-2=\frac{13}{15}-\frac{30}{15}=-\frac{17}{15}\)

c) \(3-\frac{3}{8}=\frac{24}{8}-\frac{3}{8}=\frac{21}{8}\)

d) \(\frac{1}{8}+\frac{3}{4}-\frac{1}{6}=\left(\frac{1}{8}+\frac{6}{8}\right)-\frac{8}{48}=\frac{7}{8}-\frac{8}{48}=\frac{42}{48}-\frac{8}{48}=\frac{34}{48}=\frac{17}{24}\)

e) \(\frac{12}{5}-\frac{2}{2}+\frac{7}{7}-\frac{6}{6}=\frac{12}{5}-1+1-1=\frac{12}{5}-1=\frac{12}{5}-\frac{5}{5}=\frac{7}{5}\)

Bài 3 :

\(A=\frac{55}{11.16}+\frac{55}{16.21}+\frac{55}{21.26}+....+\frac{55}{36.41}\)

\(\Leftrightarrow A=11.\left(\frac{5}{11.16}+\frac{5}{16.21}+\frac{5}{21.26}+\frac{5}{26.31}+\frac{5}{31.36}+\frac{5}{36.41}\right)\)

\(\Leftrightarrow A=11.\left(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+\frac{1}{26}-\frac{1}{31}+\frac{1}{31}-\frac{1}{36}+136\right)-\frac{1}{41}\)

\(\Leftrightarrow A=11.\left(\frac{1}{11}-\frac{1}{41}\right)=11.\frac{30}{451}=\frac{30}{41}\)

Vậy : \(A=\frac{30}{41}\)

câu hỏi này ở lớp 5

TA CÓ :A=15-15/6+15/6-15/11+15/11-15/16+15/16-15/21+15/21-15/26+15/26-15/31+15/31-15/36

A=15-15/36=14,5833333 >2

Làm

Ta có :

A = 15/1.6 + 15/6.11 + 15/11.16 + 15/16.21 + 15/21.26 + 15/26.31 + 15/31.36

A = 15. ( 1/1.6 + 1/6.11 + 1/11.16 + 1/16.21 + 1/21.26 + 1/26.31 + 1/31.36 )

A = 15 . ( 1/1 - 1/6 + 1/6 - 1/11 + 1/11-1/16 + 1/16 - 1/21 + 1/21 - 1/26 + 1/26 - 1/31 + 1/31 - 1/36 )

A = 15 . ( 1 - 1/36 )

A = 15 . ( 36 /36 - 1/36 )

A = 15 . 35/36

A = 175/12

Ta có : A = 175/12 với 2

Ta quy đồng : 

+) A=  175/12 = 175.1/12.1 = 175/12

+) 2 = 2.12/1.12 = 24/12 

Mà 175/12 > 24/12

=> 175/12 > 2

=> A > 2 ( đpcm )

HỌC TỐT

\(\frac{A}{11}=\frac{5}{11.16}+\frac{5}{16.21}+\frac{5}{21.26}+\frac{5}{26.31}+\frac{5}{31.36}+\frac{5}{36.41}\)

\(\frac{A}{11}=\frac{16-11}{11.16}+\frac{21-16}{16.21}+\frac{26-21}{21.26}+...+\frac{41-36}{36.41}\)

\(\frac{A}{11}=\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+...+\frac{1}{36}-\frac{1}{41}\)

\(\frac{A}{11}=\frac{1}{11}-\frac{1}{41}=\frac{30}{11.41}\Rightarrow A=\frac{11.30}{11.41}=\frac{30}{41}\)

\(\sqrt[1]{\dfrac{2}{3}_3\dfrac{1}{2}3_3\dfrac{3}{4}^3}\)

30/41 bạn ạ

\(\dfrac{55}{11}\cdot6+\dfrac{55}{16}\cdot21+\dfrac{55}{21}\cdot26+\dfrac{55}{26}\cdot31+\dfrac{55}{31}\cdot36+\dfrac{55}{36}\cdot41=30+\dfrac{1155}{16}+\dfrac{1430}{21}+\dfrac{1705}{26}+\dfrac{1980}{31}+\dfrac{2255}{36}=\dfrac{12186720}{406224}+\dfrac{29324295}{406224}+\dfrac{27661920}{406224}+\dfrac{26638920}{406224}+\dfrac{25945920}{406224}+\dfrac{25445420}{406224}=\dfrac{147203195}{406224}\)

= 27 x 45 + 27 x 55

= 27 x (45 + 55)

= 27 x 100

= 2700

a) \(S4=\frac{3}{50}+\frac{3}{150}+\frac{3}{300}+...+\frac{3}{9500}\)

\(S4=\frac{3}{5.10}+\frac{3}{10.15}+\frac{3}{15.20}+...+\frac{3}{95.100}\)

\(S4=\frac{3}{5}\left(\frac{1}{5}-\frac{1}{10}+\frac{1}{10}-\frac{1}{15}+\frac{1}{15}-\frac{1}{20}+...+\frac{1}{95}-\frac{1}{100}\right)\)

\(S4=\frac{3}{5}\left(\frac{1}{5}-\frac{1}{100}\right)\)

\(S4=\frac{3}{5}.\frac{19}{100}\)

\(S4=\frac{57}{500}\Rightarrow S=\frac{57}{500}:4=\frac{57}{2000}\)

b) \(S5=\frac{55}{11.16}+\frac{55}{16.21}+...+\frac{55}{36.41}\)

\(S5=\frac{55}{5}.\left(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+...+\frac{1}{36}-\frac{1}{41}\right)\)

\(S5=11.\left(\frac{1}{11}-\frac{1}{41}\right)\)

\(S5=11.\frac{30}{451}\)

\(S5=\frac{30}{41}\Rightarrow S=\frac{30}{41}:5=\frac{6}{41}\)

Mình không hiểu ý bạn là S.4 hay là S4 là tên