1/Tính bằng cách thuận tiện nhất:
a) (98,7 + 123 ) + 1,3
b) 4*23*25
c) 1/15 + 1/14 + 14/15
d) 3*21 + 4*21 + 21*93
tính bằng cách thuận tiện nhất:
a,7/4 x 11/21 + 11/21 x 5/4
b,23/14 x 6/13 -9/14 x 6/13
a, = \(\frac{11}{21}\)x \(\left(\frac{7}{4}+\frac{5}{4}\right)\)
= \(\frac{11}{21}\)x 3
= \(\frac{33}{21}\)
b) = \(\left(\frac{23}{14}-\frac{9}{14}\right)\)x \(\frac{6}{13}\)
= 1 x \(\frac{6}{13}\)
= \(\frac{6}{13}\)
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Tính bằng các thuận tiện nhất: A) 6/7 nhân 16/15 nhân 7/6 nhân 21/32, B) 21/17 nhân 13/14 nhân 56 nhân 3/42, C) 7/4 nhân 11/21+ 11/21 nhân 5/4, D) 23/14 nhân 6/13- 9/14 nhân 6/13 đang cần rất rất rất gấp đó nhanh lên
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a: \(\dfrac{6}{7}\cdot\dfrac{16}{15}\cdot\dfrac{7}{6}\cdot\dfrac{21}{32}=\dfrac{16}{32}\cdot\dfrac{21}{15}=\dfrac{1}{2}\cdot\dfrac{7}{5}=\dfrac{7}{10}\)
b: \(\dfrac{21}{17}\cdot\dfrac{13}{14}\cdot56\cdot\dfrac{3}{42}=\dfrac{21}{14}\cdot\dfrac{13}{17}\cdot\dfrac{1}{14}\cdot56=\dfrac{78}{17}\)
c: \(=\dfrac{11}{21}\left(\dfrac{7}{4}+\dfrac{5}{4}\right)=\dfrac{11}{21}\cdot3=\dfrac{11}{7}\)
1,x/7 x 4/9 x 5 = 3x4x5/7x9
2, tích của 2 phân số tối giản có tử số khác 1 = 6/35 . Tìm tổng của 2 phân số ?
3, tính = cách thuận tiện nhất
a, 6/7 x 16/15 x 7/6 x 21/32 =.....................................
b, 21/17 x 13/14 x 56 x 3/42 =.................................
c, 7/4 x 11/21 + 11/21 x 5/4 =...........................
d, 23/14 x 6/13 - 9/14 x 6/13 =.............................
Bài 3. Một hình bình hành có chiều cao là 5/7 m. Độ dài đáy gấp hai lần chiều cao, cạnh bên là 6/7m. Tính chu vi của hình bình hành.
Bài 4. Tính bằng cách thuận tiện nhất
a) 7/4 x 11/21 + 11/21 x 5/4 =
b) 23/14 x 6/13 - 9/14 x 6/13 =
Bài 4:
a: \(=\dfrac{11}{21}\left(\dfrac{7}{4}+\dfrac{5}{4}\right)=\dfrac{11}{21}\cdot3=\dfrac{11}{7}\)
b: \(=\dfrac{6}{13}\left(\dfrac{23}{14}-\dfrac{9}{14}\right)=\dfrac{6}{13}\)
Bài 3. Một hình bình hành có chiều cao là 5/7 m. Độ dài đáy gấp hai lần chiều cao, cạnh bên là 6/7m. Tính chu vi của hình bình hành.
Bài 4. Tính bằng cách thuận tiện nhất
a) 7/4 x 11/21 + 11/21 x 5/4 =
b) 23/14 x 6/13 - 9/14 x 6/13 =
Bài 4:
a: =11/21(7/4+5/4)=11/21x3=11/7
b: =6/13(23/14-9/14)=6/13
tính bằng cách thuận tiện nhất
a,\(\frac{6}{7}\cdot\frac{16}{15}\cdot\frac{7}{6}\cdot\frac{21}{32}\)b, \(\frac{21}{17}\cdot\frac{13}{14}\cdot56\cdot\frac{3}{42}\) c,\(\frac{7}{4}\cdot\frac{11}{21}+\frac{11}{21}\cdot\frac{5}{4}\) d,\(\frac{23}{14}\cdot\frac{6}{14}-\frac{9}{14}\cdot\frac{6}{13}\)
a, \(\frac{6}{7}.\frac{16}{15}.\frac{7}{6}.\frac{21}{32}=\frac{6}{7}.\frac{7}{6}.\frac{16}{15}.\frac{21}{32}\)=\(1.\frac{16}{15}.\frac{21}{32}=\frac{7}{5.2}=\frac{7}{10}\)
Phần b T2
c,\(\frac{7}{4}.\frac{11}{21}+\frac{11}{21}.\frac{5}{4}=\frac{11}{21}.\left(\frac{7}{4}+\frac{5}{4}\right)\)=\(\frac{11}{21}.3=\frac{11}{7}\)
Tính bằng cách thuân tiện nhất
A. 14/15 * 23/21 * 15/23
B. 1/2 * 9/10 + 1/2 * 8/10 - 1/2 * 7/10
A. = 14/15 * 15/23 * 23/21
= 14/23 * 23/21
= 14/21
B. = 1/2 * (9/10 + 8/10 - 7/10)
= 1/2 * 10/10
= 1/2 * 1
= 1/2
a) \(\frac{14}{15}\cdot\frac{23}{21}\cdot\frac{15}{23}=\frac{14}{21}=\frac{2}{3}\)
b)\(\frac{1}{2}\cdot\frac{9}{10}+\frac{1}{2}\cdot\frac{8}{10}-\frac{1}{2}\cdot\frac{7}{10}=\frac{1}{2}\cdot\left(\frac{9}{10}+\frac{8}{10}-\frac{7}{10}\right)=\frac{1}{2}\cdot1=\frac{1}{2}\)
1) Chứng minh rằng các số sau đây là hợp số
a) 1+2^7+3^11+5^13+7^17+11^19
b) 21^123+23^124+25
c) 425^25-37^15
d) 195^354-151^25
Tính biểu thức sau bằng cách thuận tiện nhất :
19 + 18 + 17 + 16 + 14 + 21 + 22 + 23 + 24 + 26
a. 19 + 18 + 17 + 16 + 14 + 21 + 22 + 23 + 24 + 26
= (19 + 21) + (18 + 22) + (17 + 23) + (16 + 24) + (14 + 26)
= 40 + 40 + 40 + 40 + 40
= 40 x 5
= 200