6.9+4.8+3.1 0.456+6.22+3.78 15.89+(6.75-5.89)
4.02+5.4+0.98 5.17-1.8-3.2 13.75-(3.75+6.48)
3.68+7.56-2.68 7.85+2.34-0.85+4.66 35.6-1.8-15.6-7.2
3.82+2.9+0.18+9.1 9.6+4.8-3.6 7.14-0.53-2.47
5.27+2.86-0.66+1.63 13.35-4.68+2.65 73.8-1.64-13.8-5.36
47.8-7.45+8.8 0.398+0.36+3.64 15.75+3.59-0.59+14.25
66.86-8.66-1.34 0.25×16.2×4 (1.25-0.125)×8
3.6×102 3.72×3.5+6.28×3.5 36.8-3.9-6.1
15.6×13.1-15.6-15.6×2.1 4.8×7.8+78×0.52 32+4.9-0.9
4.8×100.1 56.5×9.9+56.5 7.09×10.8-0.8×7.09
25.48-(9.4-0.52) 4.2÷3.5 320÷1.25÷8
18.76×9.9+18.76 3.52÷2.5÷0.4 3.9-4.1+6.1-5.9
5.6÷3.5 9.6÷0.8÷0.4 4.2×99+4.2
17.8÷(1.78×4) 0.49÷1.4 1.25×2.5×32 3.65×10.1
15.2÷0.25÷4 0.89×100.1 146.5-(23+46.5)
3.83×4.56+3.83×5.44 4.36×12.5×8 9.7×99+9.7
27.5×3.7-7.5×3.7 8.54÷2.5÷0.4 0.65×101 3.2×0.25×12.5
(45.9-32.7)÷8÷0.125 3.14×0.68+31.4×0.032 5.6÷1.25÷0.8÷2.5÷0.4
7.2×0.2+2.4×1.4 8.9×1.01 7.74×(2.8-1.3)+1.5×2.26
3.9×2.7+3.9×7.3 18-1.8÷0.125÷0.8 12.7×9.9+1.27
21×(9.3-3.7)-5.6 15.02-6.8-1.02 5.4×11-5.4
2.3×16+2.3×23+2.3 9.43-(6.28-1.57) 3.65×4.7-36.5×0.37
46×57+23×86 13.7×0.25-3.7÷4 2.22×9.9+6.66×6.7
101×0.87-0.91×87 10.7×16.1-15.1×10.7 0.79×199
4.8+8.63+5.2+0.37 5.93+0.19+2.81 1.76+0.195+3.24
2.35+1.713+0.287+7.65 1.57+0.245+7.43 6.02+3.6+1.98
0.134+2.66+0.866 1.27+3.9+0.73+16.1 7.5+4.9-6.5
3.07-0.38-1.62 1.29+3.7+2.71+6.3 8-2.45-1.55
3.25+1.79-0.59+1.75 23.4-0.8-13.4-7.2 0.32×403
3.2+0.36+4.8+1.64 1.23+3.4-0.23+6.6 0.25×36
12.7-(3.7+0.84) 36.54-1.76-4.54 0.25×0.73×4
7.6×0.8+0.2×7.6 0.85×199 0.25×8.5×4
1.28×8.6+0.72×8.6 12.5×0.96×0.8 10.4-9.6×0.35
0.8×(4.3×1.25) 3.12+3.12×99 28.6×101-28.6
0.86×15.7-0.86×14.7 2.4×102 2.31×1.2×0.5
14-7.32-2.68 2.64+8.67+7.36+11.33 70÷28
(2.5-0.25)×0.4 9.16×1.5-0.5×9.16 3.6-3.6×0.5
63.4÷2.5÷0.4 4.9÷1.4 3.9÷(1.3×5)
(7.7+1.54)÷0.7 2.5×2.4 2.7÷45 15÷(0.15×0.4)
0.35×1.25×2×0.8 32.4×0.9+0.1×32.4 15÷0.25
4.5÷1.8 4.2÷3.5 930÷0.6÷5
这个很简单即使1+2+3+4+5+6+7+8+9+...........+100=(100+0)+(99+1)+(98+2)+(97+3)+(96+4)............+(49+51)+50=5050
就是把这些数凑成两两相加合为一百
共可以凑五十组
另加一个五十 结果就出来了
若果你数学成绩好的话、、应该可以理解
用N来表示计算的个数,
S(总和)=(A1+An)* N/2 (只适用于等差数列,如1,2,3,4 相邻的数差相同)
S(总和)=(A1-An*q)/(1-q) (只适用于等比数列,如1,2,4,8相邻两个数的比相等)
还有其他问题再详细说
1+2=3
3+3+4=10
10+5+6=21
21+7+8=36
36+9+10=55
55+11+12=78
78+13+14=105
105+15+16=136
136+17+18=170
170+19+20=209
209+21+22=252
252+23+24=299
299+25+26=350
350+27+28=405
405+29+30=465
465+31+32=528
528+33+34=595
595+35+36=666
666+37+38=..............加下去 学会心算 很快的
1+2+3+4+5+6+7+8...+100 你再用100+99+98.。。。+1与之并列,上下相加。
100+99+98.。。。+1,得出是100个10100,再用10100除以2就是结果5050.