1. Add "+"or "-"between 1, 2, 3, 4 and 5 to make the calculation result equal to:
①5; ②6; ③7; ④8; ⑤9; ⑥ 10。
2. Add "+"or "-"between 1, 2, 3, 4, 5 and 6 to make the calculation result equal to:
① 1? 2? 3 4 5 6=9
② 1 2 ? 3 4 5 6=66
3. Add "+"or "-"between 1, 2, 3, 4, 5, 6 and 7 to make the formula hold.
? 1 2 3 4=5 6 7
4. Add "+"or "-"between 1, 2, 3, 4, 5, 6, 7, 8 and 9 to make the formula hold:
? 1 2 3 4 5=6 7 8 9 ?
? The above four topics involve the most basic number 1 ~ 5 or 1 ~ 9, and the most important addition and subtraction. For students or adults in primary school, junior high school and senior high school, they need to "think" (there is a saying that "nothing is impossible") in order to go on. This is different from the problem that the formula given in the general workbook only calculates the results, and it is more necessary to "try" to achieve "balance" here! Maybe there is more than one answer? Give at least one answer to each of the following questions. The explanation varies from person to person? May you approach the optimization of cognitive level and make the process of "thinking" and other fields more interesting and valuable. (Junior and senior high school students can discuss "permutation and combination" such as "1+2+3-4-5=-3", which is also a good classification discussion for "+"and "-"...)
Reference answer:
1, ① 1+2+3+4-5=5 or 1-2-3+4+5=5.
? ② 12+3-4-5=6
? ③ 1+2+3-4+5=7
? ④ 12-3+4-5=8
? ⑤ 1+2-3+4+5=9
? ⑥ 12-3-4+5= 10
2、? ① 1+2+3+4+5-6=9 or? 1-2+3-4+5+6=9
② 1+2+3+4+56=66 or 12+3+45+6=66.
3. 1+2-3+4=5+6-7 or 1-2+3+4=5-6+7.
4. 12+3+4-5=6+7-8+9 or 12-3-4-5=6-7-8+9 or12+3-4+5 = 6-7+8+.
Attach another expression:
Exercise the brain.
1, fill in the numbers so that the sum of 3 numbers in each row is equal to? The number in the room.
? (5)—(? )—(? )
? l？ leave
? (? ) ? (7)
? l？ |
? (8)—( )—(4)
14
2. Word of mouth ...
(1) Think about it, the 23rd picture is ().
(2) The 4th1digit is ().
3. Known: Ф+Ф = 24, Ф = Ф+Ф? . ? So:
Mouth? =( )
〇 =( )
4. There is a box of pens on the back of the card. The value of pens and boxes is 18 yuan, and pens are more expensive than boxes 14 yuan.
? Box () yuan
Pen () yuan
5.6 = 9 ... Hey, when the maximum remainder is (), the dividend is ().
6.X3 = 0x9, and () 0.
A.C.=？ incomparable
Note: In this question, 0 and 0 are natural numbers.
This "brain" question is also easy to get an answer in primary schools, which may be more conducive to the different explanations of "brain" and "appropriate" without giving an answer. For example, if you remove the "notes" of six questions, you can explore all the middle and high schools, so it is not a multiple-choice question. It can also be varied, such as "6" and "9" in 5 questions.
Swap places and so on ...
? References:
1, mathematics for top students, third edition.
2, "One Roll Done" Mathematics 5th Edition.
?
? Bai 2022. 1.4.