Tính nhanh :
$\frac{4}{5}$ – $\frac{2}{3}$ + $\frac{1}{5}$ – $\frac{1}{3}$
$\frac{2}{5}$ x $\frac{7}{4}$ – $\frac{2}{5}$ x $\frac{3}{7}$
$\frac{13}{4}$ x $\frac{2}{3}$ x $\frac{4}{13}$ x $\frac{3}{2}$
$\frac{2}{3}$ x $\frac{3}{4}$ x $\frac{4}{5}$ x $\frac{5}{6}$
$\frac{2}{5}$ + $\frac{6}{9}$ + $\frac{3}{4}$ + $\frac{3}{5}$ + $\frac{1}{3}$ + $\frac{1}{4}$
$\frac{75}{100}$ + $\frac{18}{21}$ + $\frac{19}{32}$ + $\frac{1}{4}$ + $\frac{3}{21}$ + $\frac{13}{32}$
Tính nhanh : $\frac{4}{5}$ – $\frac{2}{3}$ + $\frac{1}{5}$ – $\frac{1}{3}$ $\frac{2}{5}$ x $\frac{7}{4}$ – $\frac{2}{5}$ x $\frac{3}{7}$ $\frac{13}{4
By Nevaeh
a.4/5-2/3+1/5-1/3
=(4/5+1/5)-(2/3+1/3)
=5/5-3/3
=1-1
=0
b.2/5×7/4-2/5×3/7
=2/5×(7/4-3/7)
=2/5×37/28
=37/70
c.13/4×2/3×4/13×3/2
=(13/4×4/13)×(2/3×3/2)
=1×1
=1
d.2/3×3/4×4/5×5/6
=2/6
e.2/5+6/9+3/4+3/5+1/3+1/4
=(2/5+3/5)+(6/9+1/3)+(3/4+1/4)
=5/5+9/9+4/4
=1+1+1
=3
f.75/100+18/21+19/32+1/4+3/21+13/32
=(75/100+1/4)+(3/21+18/21)+(19/32+13/32)
=100/100+21/21+32/32
=1+1+1
=3.
a. $\frac{4}{5}$ – $\frac{2}{3}$ + $\frac{1}{5}$ – $\frac{1}{3}$
= ( $\frac{4}{5}$ + $\frac{1}{5}$) + (-$\frac{2}{3}$ – $\frac{1}{3}$ )
= 1 – 1 = 0
b. $\frac{2}{5}$ x $\frac{7}{4}$ – $\frac{2}{5}$ x $\frac{3}{7}$
= $\frac{2}{5}$ x ( $\frac{7}{4}$ – $\frac{3}{7}$ )
= $\frac{2}{5}$ x $\frac{37}{28}$
= $\frac{37}{70}$
c. $\frac{13}{4}$ x $\frac{2}{3}$ x $\frac{4}{13}$ x $\frac{3}{2}$
= ($\frac{13}{4}$ x $\frac{4}{13}$) x ($\frac{2}{3}$ x $\frac{3}{2}$)
= 1 x 1
= 1
d. $\frac{2}{3}$ x $\frac{3}{4}$ x $\frac{4}{5}$ x $\frac{5}{6}$
Đây là phép tinh nhân phân số với phân số, nếu bạn để ý kĩ thì có trên tử với mẫu có các phần dấu nhau nên ta có thể lượt bỏ cặp số giống nhau đi được
= $\frac{2}{6}$
= $\frac{1}{3}$
e. $\frac{2}{5}$ + $\frac{6}{9}$ + $\frac{3}{4}$ + $\frac{3}{5}$ + $\frac{1}{3}$ + $\frac{1}{4}$
= ($\frac{2}{5}$ + $\frac{3}{5}$) + ($\frac{3}{4}$ + $\frac{1}{4}$ ) + ( $\frac{6}{9}$ + $\frac{1}{3}$ )
= 1 + 1 + ( $\frac{6}{9}$ + $\frac{3}{9}$
= 2 + 1
= 3
f. $\frac{75}{100}$ + $\frac{18}{21}$ + $\frac{19}{32}$ + $\frac{1}{4}$ + $\frac{3}{21}$ + $\frac{13}{32}$
= ($\frac{75}{100}$ + $\frac{1}{4}$) + ( $\frac{18}{21}$ + $\frac{3}{21}$ ) + ($\frac{19}{32}$ + $\frac{13}{32}$ )
= ($\frac{75}{100}$ + $\frac{25}{100}$) + 1 + 1
= 1 + 2
= 3