Chuyên đề thực hiện phép tính bồi dưỡng học sinh giỏi Toán 6 – 7

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1 CHUYÊN Đ : TH C HI N PHÉP TÍNH D NG 1: RÚT G N Bài 1: Th c hi n phép tính: a, 12 5 6 2 10 3 5 2 2 6 3 9 3 2 .3 4 .9 5 .7 25 .49 (2 .3) (125.7) 5 .14 + b, 18 7 3 15 15 10 15 14 13 2 .18 .3 3 .2 2 .6 3 .15.4 + + c, 6 5 9 4 12 11 4 .9 6 .120 8 .3 6 + HD : a, Ta có: 12 5 6 2 10 3 5 2 2 6 3 9 3 2 .3 4 .9 5 .7 25 .49 (2 .3) (125.7) 5 .14 + ( ) ( ) ( ) ( ) ( ) 6 2 5 2 12 5 2 2 10 3 2 2 3 12 6 3 3 9 3 3 2 .3 2 . 3 5 .7 5 . 7 2 .3 5 .7 5 .2 .7 = + ( ) ( ) ( ) 12 4 10 3 12 5 12 4 10 3 10 4 12 6 9 3 9 3 3 12 6 9 3 2 .3 3 1 5 .7 1 7 2 .3 2 .3 5 .7 5 .7 2 .3 5 .7 5 .2 .7 2 .3 5 .7 1 8 = = + + 2 2 5.6 28 3 9 9 = = b, Ta có: 18 7 3 15 15 10 15 14 13 2 .18 .3 3 .2 2 .6 3 .15.4 + + 18 7 14 3 15 15 25 17 15 15 10 15 15 14 28 25 15 15 28 2 .2 .3 .3 3 .2 2 .3 3 .2 2 .2 .3 3 .3.5.2 2 .3 3 .2 .5 + + = = + + ( ) ( ) ( ) 15 15 10 2 10 2 10 25 15 3 2 .3 2 .3 1 2 .3 1 2 41 2 .3 1 2 .5 + + = = + c, Ta có: 6 5 9 4 12 11 4 .9 6 .120 8 .3 6 + = ( ) ( ) ( ) 6 5 2 2 9 9 3 12 10 12 10 4 12 12 11 11 3 12 11 11 2 . 3 2 .3 .2 .3.5 2 .3 2 .3 .5 2 .3 2 .3 2 .3 2 .3 + + = ( ) ( ) 12 10 11 11 2 .3 1 5 2.6 4 2 .3 2.3 1 3.5 5 + = = = Bài 2: Th c hi n phép tính: a, 15 9 20 9 9 16 29 6 5.4 .9 4.3 .8 5.2 .9 7.2 .27 b, 4 2 2 3 3 2 2 .5 .11 .7 2 .5 .7 .11 c, 11 12 11 11 12 11 11 11 5 .7 5 .7 5 .7 9.5 .7 + + HD : a, Ta có: 15 9 20 9 29 16 29 6 5.4 .9 4.3 .8 5.2 .3 7.2 .27 = ( ) ( ) 29 18 2 30 18 29 20 29 16 29 18 29 16 2 2 .3 5.2 3 5.2 .3 2 .3 5.2 .3 7.2 .3 2 .3 5 7.3 = = 2 3 9 58 58 = b, Ta có: 4 2 2 3 3 2 2 .5 .11 .7 2 .5 .7 .11 = 2.11 22 5.7 35 = c, Ta có: 11 12 11 11 12 11 11 11 5 .7 5 .7 5 .7 9.5 .7 + + = ( ) ( ) 11 11 11 11 5 .7 7 1 8 4 5 .7 5 9 14 7 + = = + Bài 3: Th c hi n phép tính: a, 22 7 15 14 2 11.3 .3 9 (2.3 ) b, 10 10 10 9 9 10 2 .3 2 .3 2 .3 c, 5 4 9 10 8 8 4 .9 2.6 2 .3 6 .20 + HD : a, Ta có: 22 7 15 14 2 11.3 .3 9 (2.3 ) = ( ) 29 29 30 2 28 2 28 3 . 11 3 11.3 3 3.8 6 2 .3 2 .3 4 = = = b, Ta có: 10 10 10 9 9 10 2 .3 2 .3 2 .3 ( ) 10 9 9 10 2 .3 3 1 2.2 4 2 .3 3 3 = = = c, Ta có: 5 4 9 10 8 8 4 .9 2.6 2 .3 6 .20 + ( ) ( ) 10 8 10 8 10 9 10 8 10 8 10 8 2 .3 1 3 2 .3 2 .3 2 1 2 .3 2 .3 .5 2 .3 1 5 6 3 = = = = + + Bài 4: Th c hi n phép tính: a, 12 5 6 2 10 3 5 2 2 6 4 5 3 9 3 2 .3 4 .9 5 .7 25 .49 (2 .3) 8 .3 (125.7) 5 .14 + + b, 15 9 20 9 9 19 29 6 5.4 .9 4.3 .8 5.2 .6 7.2 .27 c, 5 4 9 10 8 8 4 .9 2.6 2 .3 6 .20 + HD:2 a, Ta có : 12 5 6 2 10 3 5 2 2 6 4 5 3 9 3 2 .3 4 .9 5 .7 25 .49 (2 .3) 8 .3 (125.7) 5 .14 + + = ( ) ( ) ( ) ( ) ( ) 12 4 10 3 12 5 12 4 10 3 10 4 12 6 12 5 9 3 9 3 3 12 5 9 3 2 .3 3 1 5 .7 1 7 5. 6 2 .3 2 .3 5 .7 5 .7 10 2 .3 2 .3 5 .7 5 .7 .2 2 .3 3 1 5 .7 1 8 9 3 = = = + + + + b, Ta có : 15 9 20 9 9 19 29 6 5.4 .9 4.3 .8 5.2 .6 7.2 .27 = ( ) ( ) 29 18 2 30 18 20 29 28 19 29 18 28 18 2 .3 5.2 3 5.2 .3 3 .2 2 2 5.2 .3 7.2 .3 2 .3 5.3 7.2 1 = = = c, Ta có : 5 4 9 10 8 8 4 .9 2.6 2 .3 6 .20 + = ( ) ( ) 10 8 10 8 10 9 10 8 10 8 10 8 2 .3 1 3 2 .3 2 .3 2 1 2 .3 2 .3 .5 2 .3 1 5 6 3 = = = + + Bài 5: Th c hi n phép tính: a, 12 7 15 8 24 14 12 5 15.4 .9 4.3 .8 19.2 .3 6.4 .27 b, 15 22 16 4 9 7 5 23 3 .2 6 .4 2.9 .8 7.27 .2 + c, 3 10 9 6 12 11 16 .3 120.6 4 .3 6 + + HD : a, Ta có: 12 7 15 8 24 14 12 5 15.4 .9 4.3 .8 19.2 .3 6.4 .27 = ( ) ( ) 24 15 2 24 15 26 15 24 14 25 16 24 24 2 2 .3 5 2 5.2 .3 2 .3 3 3 19.2 .3 2 .3 1 2 .3 19 2.3 = = = b, Ta có : 15 22 16 4 9 7 5 23 3 .2 6 .4 2.9 .8 7.27 .2 + = ( ) ( ) 22 15 2 15 22 24 16 22 18 15 23 22 15 3 2 .3 1 2 .3 3 .2 2 .3 13 13 2 .3 7.3 .2 5 5 2 .3 3 7.2 + + = = = c, Ta có: ( ) ( ) ( ) ( ) ( ) ( ) 3 9 4 10 3 12 10 12 10 12 10 6 12 12 11 11 11 11 11 2 12 2 .3 2 .3.5. 2.3 2 .3 1 5 2 .3 2 .3 .5 2.6 12 2 .3 2 .3 2 .3 2.3 1 3.7 21 2 .3 2.3 + + + = = = = + + + Bài 6: Th c hi n phép tính : a, ( ) ( ) 12 5 6 2 10 3 5 2 6 3 9 3 2 4 5 2 .3 4 .9 5 .7 25 .49 125.7 5 .14 2 .3 8 .3 A = + + b, 15 9 20 9 10 12 29 6 5.4 .9 4.3 .8 5.2 .6 7.2 .27 Bài 7: Th c hi n phép tính: a, ( ) 12 5 6 2 6 2 4 5 2 .3 4 .9 2 .3 8 .3 A = + b, 5 4 9 10 8 8 4 .9 2.6 2 .3 6 .20 B = + Bài 8: Th c hi n phép tính : a, 10 10 9 4 3 .11 3 .5 3 .2 + b, 10 10 8 2 .13 2 .65 2 .104 + Bài 9: Th c hi n phép tính: a, 30 7 13 27 27 7 10 27 2 .5 2 .5 2 .5 2 .5 + + b, ( ) ( ) ( ) 6 6 5 3 10 5 3 3 .15 9 . 15 3 .5 .2 + Bài 10: Th c hi n phép tính: a, 2 11 2 2 6 2 12 4 2 3 5 .6 .16 6 .12 .15 2.6 .10 81 .960 + b, ( ) ( ) 9 19 3 4 10 9 10 2 .27 .5 15. 4 .9 6 .2 12 A = Bài 11: Th c hi n phép tính: a, ( ) ( ) 5 15 4 10 20 6 6 3 15 0,8 2 .9 45 .5 : 6 .8 75 0,4 + b, ( ) 15 14 22 21 10 16 15 5 3.7 19.7 2.5 9.5 : 25 7 3.7 A = + Bài 12: Tính giá tr c a bi u th c: 7 3 3 7 7 7 2 9 3 .5 : 5 4 16 2 .5 512 A + = +