★ Example 1 1.24+0.78+8.76
Solution formula =( 1.24+8.76)+0.78.
= 10+0.78
= 10.78
Keys and skills to solve problems
Use the commutative law and associative law of addition, because the sum of 1.24 and 8.76 is exactly the integer 10.
★ Example 2 933- 157-43
The solution formula = 933-(157+43) = 933-200 = 733.
Keys and skills to solve problems
According to the nature of removing brackets by subtraction, you can subtract the sum of several numbers by subtracting several numbers from one number in succession. So the sum of questions 157 and 43 is exactly 200.
★ Example 3 482 1-998
=482 1- 1000+2=3823
Keys and skills to solve problems
The subtraction 998 in this problem is close to 1000, so we change it to 1000-2. According to the nature of removing brackets by subtraction, the original formula is =482 1- 1000+2, which is delicious to calculate. After skilled calculation, 998 will become 1000.
★ Example 4 0.4× 125×25×0.8
The formula = (0.4× 25 )× (125× 0.8) =10×100 =1000.
Keys and skills to solve problems
Using the commutative law and associative law of multiplication, because 0.4×25 just gets 10, 125×0.8 just gets 100.
★ Example 5 1.25×(8+ 10)
The formula =1.25× 8+1.25×10 =10+12.5 = 22.5.
Keys and skills to solve problems
According to the law of multiplication and distribution, the sum of two addends is multiplied by a number, and each addend can be multiplied by this number separately, and then the products are added.
★★★ Example 6 9 123-( 123+8.8)
The formula = 9123-123-8.8 = 9000-8.8 = 8991.2.
Keys and skills to solve problems
According to the property of removing brackets by subtraction, one number can be subtracted from the sum of several numbers continuously, because 9 123 is subtracted from 123 to get exactly 9000. It should be noted that after the brackets are removed from subtraction, the original addition of 8.8 has now become the subtraction of 8.8.
★★★ Example 71.24× 8.3+8.3×1.76
The solution formula = 8.3× (1.24+1.76) = 8.3× 3 = 24.9.
Keys and skills to solve problems
This solution is an inverse application of the laws of multiplication and distribution. That is, the sum of several numbers multiplied by a number can be multiplied by the sum of these numbers.
★★★★ Example 8 9999× 100 1
The formula = 9999× (1000+1) = 9999×1000+9999×1.
= 10008999
Keys and skills to solve problems
In this question, 100 1 is regarded as 1000+ 1, and then it is simplified according to the distribution law of multiplication.
Keys and skills to solve problems
In this problem, the distribution law of multiplication has been used twice, so we can't just be satisfied with the success of the first simple calculation, but continue to look for a reasonable and flexible algorithm until it is all over.
Keys and skills to solve problems
According to the need, this question uses subtraction twice to remove the nature of brackets.
★★★ Example114.8× 6.3-6.3× 6.5+8.3× 3.7
The solution formula is = (14.8-6.5) × 6.3+8.3 × 3.7.
=8.3×6.3+8.3×3.7
=8.3×(6.3+3.7)
=8.3× 10
=83
Keys and skills to solve problems
The 8.3×3.7 in this problem should not be mistaken for 6.3×3.7 in the first simple calculation. If you can't participate in the simple calculation for the first time, just copy it down and see if there is any chance in the future. The result of the first simple calculation is just 8.3×6.3, so that the second simple calculation can be carried out.
★★★★ ★ Example 12 32× 125×25
Solution formula =4×8× 125×25.
=(4×25)×(8× 125)
= 100× 1000
= 100000
Keys and skills to solve problems
Divide 32 into 4×8, so that 125×8 and 25×4 can get integer hundreds and integer thousands.
5.4÷ 1.8+240× 1.5
=3+360
=363
9000÷72×( 1.25×0.7×8)
=9000÷72×7
= 125×7
=875
6 1-( 1.25+2.5×0.7)
=6 1-3
=58
[( 10-0.8)+9.85]-2÷0. 125
= 19.05-2÷0. 125
= 19.05- 16
=3.05
3^2*3.25678
3^3-5
12+5268.32-2569
123+456-52*8
789+456-78
18 1+2564)+27 19
378+44+ 1 14+242+222
276+228+353+2 19
(375+ 1034)+(966+ 125)
(2 130+783+270)+ 10 17
99+999+9999+99999
7755-(2 187+755)
22 14+638+286
3065-738- 1065
138×25×4
( 13× 125)×(3×8)
( 12+24+80)×5025×32× 125
32×(25+ 125)
178× 10 1- 178
84×36+64×84
75×99+2×75
83× 102-83×2
123× 18- 123×3+85× 123
50×(34×4)×3
25×(24+ 16)
178×99+ 178
79×42+79+79×57
7300÷25÷4
8 100÷4÷75
158+262+ 138
375+2 19+38 1+225
500 1-247- 102 1-232
( 18 1+2564)+27 19
378+44+ 1 14+242+222
276+228+353+2 19
(375+ 1034)+(966+ 125)
(2 130+783+270)+ 10 17
99+999+9999+99999
7755-(2 187+755)
22 14+638+286
3065-738- 1065
2357- 183-3 17-357
2365- 1086-2 14
138×25×4
( 13× 125)×(3×8)
( 12+24+80)×50
25×32× 125
32×(25+ 125)
178× 10 1- 178
84×36+64×84
75×99+2×75
83× 102-83×2
123× 18- 123×3+85× 123
50×(34×4)×3
25×(24+ 16)
178×99+ 178
79×42+79+79×57
7300÷25÷4
8 100÷4÷75
2356-( 1356-72 1)
1235-( 1780- 1665)
75×27+ 19×2 5
3 1×870+ 13×3 10
4×(25×65+25×28)
2.73 + 0.89 + 1.27
4.37 + 0.28 + 1.63 + 5.72
10 - 0.432 - 2.568
9.3 - 5.26 - 2.74
13.4-(3.4+5.2)
14.9-(5.2+4.9)
18.32 - 5.47 - 4.32
17.29 - 5.28 - 6.29
25 × 6.8 × 0.04
0.25 × 32 × 0. 125
6.4 × 1.25 × 12.5
3.28 × 5.7 + 6.72 × 5.7
2. 1 × 99 + 2. 1
1.7 × 9.9 + 0. 17
23 × 0. 1 + 2.3 × 9.9
0. 18 +4.26 -0. 18 +4.26
0.58 × 1.3 ÷ 0.58 × 1.3
7.3 ÷4 + 2.7 × 0.25
3.75 × 0.5 - 2.75 ÷ 2
5.26 × 0. 125 + 2.74 ÷ 8
9.5 ÷( 1.9 × 8)
12.8 ÷ (0.4 × 1.6)
930 ÷ 0.6 ÷5
63.4 ÷ 2.5 ÷ 0.4
(7.7 + 1.54)÷ 0.7
( 1 1.7 + 9.9)÷ 0.9
6.9+4.8+3. 1
15.89+(6.75-5.89)
7.85+2.34-0.85+4.66
35.6- 1.8- 15.6-7.2
13.75-(3.75+6.48)
47.8-7.45+2.55
66.86-8.66- 1.34
0.25× 16.2×4
0.25×32 ×0. 125
2 .5 ×(4 +0.4)
( 1.25-0. 125)×8
56.5×9.9+56.5
5.4× 1 1-5.4
3.83×4.56+3.83×5.44
7.09× 10.8-0.8×7.09
3.65×4.7-36.5×0.37
13.7×0.25-3.7÷4
10.7× 16. 1- 1. 1× 10.7 + 10.7 ×5
3.9÷( 1.3×5)
63.4÷2.5÷0.4
(7.7+ 1.4)÷0.7
18 ÷ (9-3)
The sixth grade question is so simple? I'm in grade two.