Question

[ARKFF]

tính nhanh

a) 891 + (359 + 109)

b) \(\dfrac{19}{11}\) + ( \(\dfrac{5}{13}\) + \(\dfrac{3}{11}\))

c) \(\dfrac{17,8\cdot3,7-7,8\cdot4,8+5,7\cdot17,8-4,6\cdot7,8}{11,2+12,3+13,4-12,6-11,5-10,4}\)

Answer 1

[Nguyễn Lê Phước Thịnh]

a: 891+(359+109)

=891+109+359

=1000+359=1359

b: \(\dfrac{19}{11}+\left(\dfrac{5}{13}+\dfrac{3}{11}\right)\)

\(=\dfrac{19}{11}+\dfrac{3}{11}+\dfrac{5}{13}\)

\(=2+\dfrac{5}{13}=\dfrac{31}{13}\)

c: \(\dfrac{17,8\cdot3,7-7,8\cdot4,8+5,7\cdot17,8-4,6\cdot7,8}{11,2+12,3+13,4-12,6-11,5-10,4}\)

\(=\dfrac{17,8\left(3,7+5,7\right)-7,8\left(4,8+4,6\right)}{11,2-10,4+12,3-11,5+13,4-12,6}\)

\(=\dfrac{17,8\cdot9,4-7,8\cdot9,4}{0,8+0,8+0,8}=\dfrac{9,4\cdot10}{2,4}=\dfrac{94}{2,4}=\dfrac{940}{24}=\dfrac{235}{6}\)

Answer 2

[boi đz]

\(a,891+\left(359+109\right)\\ =\left(891+109\right)+359\\ =1000+359\\ =1359\\ b,\dfrac{19}{11}+\left(\dfrac{5}{13}+\dfrac{3}{11}\right)\\ =\left(\dfrac{19}{11}+\dfrac{3}{11}\right)+\dfrac{5}{13}\\ =2+\dfrac{5}{13}\\ =\dfrac{26}{13}+\dfrac{5}{13}\\ =\dfrac{31}{13}\\ c,\dfrac{17,8\times3,7-7,8\times4,8+5,7\cdot17,8-4,6\times7,8}{11,2+12,3+13,4-12,6-11,5-10,4}\\ =\dfrac{17,8\times\left(3,7+5,7\right)-7,8\times\left(4,8+4,6\right)}{\left(11,2+12,3-11,5\right)+\left(13,4-10,4\right)-12,6}\\ =\dfrac{17,8\times9,4-7,8\times9,4}{12+3-12,6}\\ =\dfrac{9,4\times\left(17,8-7,8\right)}{2,4}\\ =\dfrac{94}{2,4}\\ =\dfrac{940}{24}=\dfrac{235}{6}\)