Tính nhanh a) 3/13 – 21/84 + -16/13 + 1/4 – 6/15 b) 4/15 . 31/2 – 4/5 . 46/3 c) -1/4 . 152/11 – 1/4 . 68/11 giúp mi vs ạ

0 bình luận về “Tính nhanh a) 3/13 – 21/84 + -16/13 + 1/4 – 6/15 b) 4/15 . 31/2 – 4/5 . 46/3 c) -1/4 . 152/11 – 1/4 . 68/11 giúp mi vs ạ”

1. Đáp án:

    a, 3/13-21/84+(-16/13)+1/4-6/15

   = 3/13-1/4+(-16/13)+ 1/4-6/15

   = ( 3/13-16/13)+(-1/4+1/4)-6/15

   = -1-6/15

   = -7/5

   b, 4/15.31/2-4/5.46/3

   = 4/5.1/3.31/2-4/5.46/3

   = 4/5.31/6-4/5.46/3

   = 4/5.(31/6-46/3)

   = 4/5.(-61/6)

   = -122/15

   c, -1/4.152/11-1/4.68/11

   = -1/4.(152/11-68/11)

   =-1/4.84/11

   = -84/44

   = -21/11

    

   Trả lời

2. Đáp án:

   a, ,$\frac{-7}{5}$

   b,$\frac{-122}{15}$

   c,-5

   Giải thích các bước giải:

    a,$\frac{3}{13}$ – $\frac{21}{84}$ + – $\frac{16}{13}$ + $\frac{1}{4}$ – $\frac{6}{15}$ 

   = ( $\frac{3}{13}$ – $\frac{16}{13}$ ) + ( $\frac{1}{4}$ – $\frac{21}{84}$ ) – $\frac{6}{15}$ 

   = -1 + 0 – $\frac{6}{15}$

   = $\frac{-7}{5}$

   b,$\frac{4}{15}$×$\frac{31}{2}$ – $\frac{4}{5}$× $\frac{46}{3}$

   = $\frac{4×2}{15×2}$×$\frac{31×15}{2×15}$ – $\frac{4×6}{5×6}$× $\frac{46×10}{3×10}$

   = $\frac{8}{30}$×$\frac{465}{30}$ – $\frac{24}{30}$× $\frac{460}{30}$

   = $\frac{62}{15}$ – $\frac{184}{15}$ 

   = ,$\frac{-122}{15}$

   c,$\frac{-1}{4}$×$\frac{152}{11}$ – $\frac{1}{4}$× $\frac{68}{11}$

   = $\frac{-1}{4}$ × ( $\frac{152}{11}$ + $\frac{68}{11}$ )

   = $\frac{-1}{4}$ × 20 

   = -5

   Trả lời