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Tính nhanh:
a) (-6,37 × 0,4) × 2,5;
b) (-0,125) × (-5,3) × 8;
c) (-2,5) × (-4) × (-7,9);
d) (-0,375) × 413(−2)3413(−2)3
Hướng dẫn làm bài:
a) (- 6,37 × 0,4) × 2,5
= - 6,37× (0,4 × 2,5)
= - 6,37 × 1 = - 6,37
b) (-0,125) × (-5,3) × 8
= (-0,125 × 8) × (-5,3)
=(-1). (-5,3) = 5,3
c) (-2,5) × (-4) × (-7,9)
= [(-2,5) × (-4)] × (-7,9)
= 10 . (-7,9)
= -79
d) (−0,375).413.(−2)3
=[(−0,375).(−8)].133=[(−0,375).(−8)].133
=3.133=13
a) \(=\left(\frac{-337}{100}:\frac{40}{100}\right).\frac{250}{100}=\frac{-337}{40}.\frac{40}{16}=-\frac{337}{16}\)
b) \(=\frac{-1}{8}.\left(-5,3\right).8=\frac{-1}{8}.8.\left(-5,3\right)=-1.\left(-5,3\right)=5,3\)
c) \(=10.\left(-7,9\right)=-79\)
d) \(=-\frac{3}{8}.\frac{13}{3}.\left(-8\right)=\left[-\frac{3}{8}.\left(-8\right)\right].\frac{13}{3}=3.\frac{13}{3}=13\)
a)(-3,37:0,4).2,5
=(-8,425).2,5
=-21,0625
b) (-0,125) . (-5,3) . 8
=(-0,125).8.(-5,3)
=(-1).(-5,3)
=5,3
c)(-2,5).(-4).(-7,9)
=10.(-7,9)
=-79
d)(-0,375).\(4\frac{1}{3}\).(-2)3
=(-0,375).(-2)3.\(4\frac{1}{3}\)
=3.\(\frac{13}{3}\)
=13
a)
\(\left(-6,37.0,4\right)2,5=\left(-6,37\right).\left(\frac{2}{5}.\frac{5}{2}\right)=1.\left(-6,37\right)=-6,37\)
b)
\(\left(-0,125\right)\left(-5,3\right).8=\left[\left(-\frac{1}{8}\right).8\right]\left(-5,3\right)=\left(-1\right)\left(-5,3\right)=5,3\)
c)
\(\left(-2,5\right).\left(-4\right).\left(-7,9\right)=\left[\left(-\frac{5}{2}\right).\left(-4\right)\right]\left(-7,9\right)=10.\left(-7,9\right)=-79\)
d)
\(\left(-0,375\right).4\frac{1}{3}.\left(-2\right)^3=\left(-\frac{3}{8}\right).\frac{12}{3}.\left(-8\right)=12\)
a) ( -6,37 . 0,4 ) . 2,5
= -6,37 . ( 0,4 . 2,5 )
= -6,37 . 1
= -6,37
b) ( -0,125 ) . ( 5,3 ) . 8
= ( -0,125 . 8 ) . 5,3
= -1 . 5,3
= -5,3
c) ( -2,5 ) . ( -4 ) . ( -7,9 )
= ( -2,5 . -4 ) . -7,9
= -10 . -7,9
= 79
A = \(\left(3,1-2,5\right)-\left(-2,5+3,1\right)\)
\(=3,1-2,5+2,5-3,1=6,2\)
B = \(\left(5,3-2,8\right)-\left(4+5,3\right)\)
\(=5,3-2,8-4-5,3=-6,8\)
C = \(-\left(251.3+281\right)+3.251-\left(1-281\right)\)
\(=-251.3-281+3.251-1+281=-1\)
D = \(-\left(\frac{3}{5}+\frac{3}{4}\right)-\left(-\frac{3}{4}+\frac{2}{5}\right)\)
\(=-\frac{3}{5}-\frac{3}{4}+\frac{3}{4}-\frac{2}{5}=-1\)
(Nhớ k cho mình với nhá!)
Tìm x trong các tỉ lệ thức sau :
\(\left(a\right)3,8\div\left(2x\right)=\frac{1}{4}\div2\frac{2}{3}\)
\(3,8\div\left(2x\right)=\frac{3}{32}\)
\(2x=3,8\div\frac{3}{32}\)
\(2x=40\frac{8}{15}\)
\(x=20\frac{4}{15}\)
\(\left(0,25x\right)\div3=\frac{5}{6}\div0,125\)
\(\left(0,25x\right)\div3=6\frac{2}{3}\)
\(\left(0,25x\right)=6\frac{2}{5}\times3\)
\(\left(0,25x\right)=20\)
\(x=80\)
\(0,01\div2,5=\left(0,75x\right)\div0,75\)
\(0,004=\left(0,75x\right)\div0,75\)
\(0,75x=0,75\times0,004\)
\(0,75x=0,003\)
\(x=0,004\)
\(1\frac{1}{3}\div0,8=\frac{2}{3}\div\left(0,1x\right)\)
\(1\frac{2}{3}=\frac{2}{3}\div\left(0,1x\right)\)
\(\left(0,1x\right)=\frac{2}{3}\div1\frac{2}{3}\)
\(\left(0,1x\right)=\frac{2}{5}\)
\(x=4\)
Dung ko z
a) (-6,37.0,4).2,5
= (0,4.2,5).(-6,37)
= 1. (-6,37)
= -6,37
b) (-0,125).(-5,3).8
= (-0,125.8).(-5,3)
= -1. (-5,3)
= 5,3
c) (-2,5).(-4).(-7,9)
= ((-2,5).(-4)). (-7,9)
= 10. (-7,9)
= -79
d) (-0,375). \(4\frac{1}{3}\). \(\left(-2^3\right)\)
= (-0,375). \(\frac{13}{3}\). (-8)
= ((-0,375).(-8)). \(\frac{13}{3}\)
= 3. \(\frac{13}{3}\)
= 13