Grade 12/3 Compulsory Math Questions: Variations in Additive and Subtractive Equations
By addition + addition = and can be extended
Sum - plus number = plus number
It can be deduced from the subtraction to the subtraction - the subtraction = the difference
Subtraction = subtraction + difference
Subtraction - difference = subtraction,
These are also the two methods of subtraction.
Here are some of the common questions:
Students hold the blackboard in front of the blackboard with both hands
Type 1:
1. The sum of the three numbers to be subtracted, the subtraction and the difference is 10, the subtraction is 3, and what is the subtracted number?
I believe that everyone will soon be able to figure it out: the subtraction is 5.
Because the subtraction = subtraction + difference, the sum of the three numbers of subtracted, subtracted and difference is 10;
Therefore, 2 subtractions are 10, and 1 subtraction is 5.
2, the sum of the three numbers of subtraction, subtraction and difference is 100, the difference is 32, and the subtraction is what?
I believe that you will soon be able to figure it out: the subtraction is 18.
Because the subtracted number = subtraction + difference, the sum of the three numbers of subtracted, subtracted and difference is 100;
Therefore, 2 subtractions are 100, and 1 subtraction is 50.
Subtraction = subtraction - difference = 50-32 = 18
3, the sum of the three numbers of subtraction, subtraction and difference is 1000, the subtraction is 332, the difference is what?
I believe that everyone will soon be able to figure it out: the difference is 168.
Because the subtraction = subtraction + difference, the sum of the three numbers of subtraction, subtraction and difference is 1000;
Therefore, 2 subtractions are 1000 and 1 subtraction is 500.
Difference = subtraction - subtraction = 500-332 = 168
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Solution idea: divide the total number equally, find out the subtraction, and then find the difference according to the subtraction, the subtraction or the subtraction, the difference.
When parents have told their children about this kind of problem, they must first turn the number in the problem into a small number, so that the child will be easier to calculate, and when explaining the idea of the problem to the child, they should also give different examples, first let the child try to make it, and finally summarize the idea of solving the problem.
Type 2: Variation in additive equation
1. When Xiaoqing calculates an additive equation, he writes 6 as 9, and the result obtained is 10, what is the correct result?
Because the addition number = sum - adds, to get the correct result, you must first find one of the addition numbers, and then add the correct number.
First find the correct addition number: 10-9=1
Then find the correct sum: 1 + 6 = 7
Comprehensive calculation: 10-9 + 6 = 7
2. When Xiaoqing calculates an additive equation, he writes 43 as 34, and the result obtained is 66, what is the correct result?
First find the correct addition: 66-34=-32
Then find the correct sum: 32 + 43 = 75
Comprehensive calculation: 66-34 + 43 = 75
Solution: First use and subtract the wrong addition, plus the correct addition.
Type 3: Variation in subtractive formula
1. When Xiao Min calculates a subtractive formula, he writes the subtracted number 9 as 6, and the result obtained is 5, what is the correct result?
Because the difference = subtraction - subtraction, to get the correct result, first find the correct subtraction, and then subtract the correct subtraction from the subtracted number.
First find the correct subtraction: 6-5=1
Then find the correct difference: 9-6=3
Comprehensive equation: 9-(6-5)=8
Variant: When Xiao Min calculates a subtraction equation, he writes the subtracted number 96 as 69, and the result is 15, what is the correct result?
96-（69-15）=42
Solution: First calculate the correct subtraction, and then use the subtraction to subtract the correct subtraction.
2. When Xiao Min calculates a subtraction equation, he writes the subtraction 9 as 6, and the result obtained is 3, what is the correct result?
Because the difference = subtraction - subtraction, to get the correct result, first find the subtraction, and then subtract the correct subtraction from the subtracted number.
First find the subtraction: 3 + 6 = 9
Then find the correct difference: 9-9=0
Comprehensive calculation: 3 + 6-9 = 0
Variant: When Xiao Min calculates a subtraction equation, he writes the subtraction 16 as 61, and the result is 7, what is the correct result?
7+61-16=52
Solution: First calculate the subtracted number, and then use the subtracted number to subtract the correct subtraction.
Type 4:
In the addition equation, the addition number decreases, and decreases;
1. When Xiao Min calculates an additive equation, he writes an 8 with an additive number of bits as 3, and the result is 88, what is the correct result?
The number 8 of the addition is written as 3, so the sum is reduced by 8-3 = 5
88+（8-3）=93
Variant: When Xiao Min calculates an additive equation, he writes an 8 with dozens of digits as 3, and the result is 88, what is the correct result?
Write the ten bits of 8 of the addition number as 3, so the sum reduction is 80-30 = 50
88+（8-3）×10=138
In the additive equation, the addition number increases, and the number increases.
2. When Calculating an Additive Equation, Yin Miao writes an addition number of 6 as 9, and the result is 60, what is the correct result?
The bit 6 of the addition is written as 9, so the sum is increased by 9-6 =3
60-（9-6）=57
Variant: When Yin Miao calculates an additive equation, writes a 6 with dozens of digits as 9, and the result is 160, what is the correct result?
Write the ten bits of 6 of the addition number as 9, so the sum is increased by 90-60 = 30
160-（90-60）=130
Comprehensive Exercises:
When Yin Miao calculates an additive equation, writes an 8 with an additive number of digits as 3, and a 2 with dozens of digits as 5, and the result is 88.
88+（8-3）-（50-20）=63
Solution idea: who increases will subtract the increased number, and whoever decreases will add the decreased number.
Type five
In the subtraction equation, the subtracted number increases and the difference increases
1. When Xiaoming calculates a subtractive formula, he writes the 5 of the subtracted digits as 7, and the result obtained is 8, what is the correct result?
Write the minused bit 5 as 7, so the difference increases by 7-5=2
8-（7-5）=6
In the subtraction equation, the subtracted number is reduced, the difference is reduced,
2. When Xiaoming calculates a subtractive formula, he writes the 9 of the decremented number of ten digits as 6, and the result obtained is 10, what is the correct result?
Write the 9 of the ten digits of the subtracted number as 6, so the difference is reduced by 90-60 = 30
10+（90-60）=40
Type six
In the subtractive equation, the subtraction increases and the difference decreases
1. When Xiao Min calculates a subtraction formula, he writes the 2 of the ten digits of the subtraction as 5, and the result obtained is 8, what is the correct result?
Write 2 of the ten digits of the subtraction as 5, so the difference is reduced by 50-20 = 30
8+（50-20）=38
In the subtraction equation, the subtraction decreases and the difference increases
2. When Xiao Min calculates a subtraction equation, the result obtained by writing the 9 of the ten digits of the subtraction as 6 is 100, what is the correct result?
Write 9 of the ten digits of the minus as 6, so the difference increases by 90-60=30
100-（90-60）=70
Comprehensive exercises
When Yin Miao calculates a subtraction equation, he writes the 8 of the subtracted digits as 3, and the 2 of the minus of the ten digits as 5, and the result is 18, what is the correct result?
18+（8-3）+（50-20）=53
When Xiaoming calculates a subtraction equation, he writes the 5 of the subtracted digits as 7, and the 7 of the subtractive ten digits as 1, and the result is 88, what is the correct result?
88-（7-5）-（70-10）=26
The questions for different grades did not change much except for the change in the size of the digits and values. Parents can practice for their children according to different types of questions.