0.6 1×0.25+0. 18× 1/4+0.2 1×25/ 100
= 0.6 1× 1/4+0. 18× 1/4+0.2 1× 1/4
= 1/4 ×(0.6 1+0. 18+0.2 1)
= 1/4 × 1
= 1/4
9999×7+ 1 1 1 1×37
= 1 1 1 1×9×7+ 1 1 1 1×37
= 1 1 1 1×63+ 1 1 1 1×37
= 1 1 1 1×(63+37)
= 1 1 1 1× 100
= 1 1 1 100
999×778+333×666
=999×778+333×3×222
=999 ×778+999×222
=999×(778+222)
=999× 1000
=999000
20022002/200 1200 1
=2002× 1000 1/200 1× 1000 1
=2002/200 1
231231and 23 1/232
==23 1÷(23 1+23 1/232)
=23 1÷[23 1×( 1+ 1/232)]
= 1÷( 1+ 1/232)
= 1÷(233/232)
=232/233
As can be seen from the above questions, the skills and methods of simple calculation are the same regardless of new questions or ordinary questions, which need to be observed frequently. The simple calculation method in primary school is to use the learned algorithm, which can make the calculation process simple and not easy to make mistakes. The specific summary is as follows:
1. When a simple calculation problem has only one-level operation (only multiplication and division or only addition and subtraction) and no brackets, it can be "moved with signs". such as
(a+b+c=a+c+b，a+b-c=a-c+b，a-b+c=a+c-b，a-b-c = a-c-b； a×b×c=a×c×b，a \b \c = a \c \b，a×b \c = a \c×b，a \b×c = a×c \b)
2. Add parentheses to simplify the calculation:
When there are only addition and subtraction operations without brackets in simple calculation problems, parentheses can be added directly after the plus sign. The operations in parentheses are addition or addition, subtraction or subtraction. But when parentheses are added after the MINUS sign, the operation in parentheses, which used to be addition, will now become subtraction; It used to be a decrease, but now it will become an increase; For example:
a+b+c=a+ (b + c)，a+b-c=a +(b-c)，a-b+c = a-(b-c)，a-b-c = a-(b+c)；
Similarly, when there are only multiplication and division operations without parentheses in simple calculation problems, parentheses can be added directly after the multiplication sign, and the operations in parentheses are multiplication or multiplication, division or division. But when parentheses are added after the division symbol, the operation in parentheses was originally multiplication, and now it will become division; It used to be division, but now it's multiplication. For example:
a×b×c=a×(b×c)，a×b÷c=a×(b÷c)，a÷b÷c=a÷(b×c)，a÷b×c=a÷(b÷c
3. Remove the brackets to simplify the calculation:
When there are only addition and subtraction operations and brackets in simple calculation problems, you can directly remove the brackets after the plus sign, indicating that you are adding or adding or subtracting now. But when the brackets after the minus sign are removed, the addition in the original brackets will now be reduced; It used to be negative, but now it is positive. For example:
a+(b+ c)= a+b+ c； a+(b-c)= a+b-c； a-(B- c)= a-b+ c； a-(b+ c)= a-b-c；
Similarly, when there are only multiplication and division operations and brackets in a simple calculation problem, you can directly remove the brackets after the multiplication sign, which becomes multiplication or multiplication, division or division. But when the brackets after the division sign are removed, the multiplication in the original brackets will be removed now; It used to be division, but now it's multiplication. For example:
a×(b×c)= a×b×c； a×(b÷c)= a×b÷c； a \(b×c)= a \b \c； a \(b \c)= a \b×c；
4. Two typical laws of multiplication and distribution.
One is the addition and subtraction operation in brackets, which is multiplied by another number, paying attention to the distribution;
The other is to pay attention to the extraction of the same factor; The above example (0.61× 0.25+0.18×1/4+0.21× 25/100).
5. There are some simple skills.
(1) Clever loan: (for example, 9999+999+9 =10000-1000-1+/kloc-0.
(2) Do not change the digital partition, as shown in the above example (999×778+333×666).
(3) Clever division into multiplication
(4) Pay attention to the structure to make the formula conform to the conditions of multiplication and division; The above example (9999× 7+1111× 37).