0

0

1-6 1 + 42 1 + 56 1 + 72 1
=1-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1-1/9
=8/9

Add operation symbols and parentheses to make the equation true. 34 563 16 = 26, the order of numbers cannot be changed Another question, 62 35 7 12 3 = 21

34-56÷(3+1)+6=26

Simple calculation of 1 / 6 + 1 / 12 + 1 / 20 + 1 / 30 + 1 / 42 + 1 / 56 + 1 / 72 + 1 / 90

1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)+(1/9-1/10)=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10=1/2-1/10=2/5

*Represents a new operation symbol, 2 * 3 = 2 + 3 + 4, 7 * 2 = 7 + 8, 5 * 6 =?

M * n represents the sum of N consecutive integers from m, such as 2 * 3 = 2 + 3 + 4, 7 * 2 = 7 + 8
So 5 * 6 = 5 + 6 + 7 + 8 + 9 + 10 = 45

In this paper, a new symbol of operation is given, which is called "2 + 3 + 4", 7 ﹥ 2 = 7 + 8, 3 ﹥ 5 = 3 + 4 + 5 + 6 + 7. According to this rule, 10 ﹤ 4=______ .

10◎4
=10+11+12+13
=46
So the answer is: 46

"*" is a kind of operation symbol, known as 2 * 3 = 2 + 3 + 4, 7 * 2 = 7 + 8?

0

0

10◎4
=10+11+12+13
=46
So the answer is: 46

@Denotes a new operation symbol 2@3=2+3+4 , 7@2=7+8 , 3@5=3+4+5+6+7 According to the law 5@8 What is the value of?

5@8
=5+6+7+8+9+10+11+12
=(5+12)*8/2
=17*4
=68

'∮ denotes a new operation symbol. We know that 2 ∮ 3 = 2 + 3 + 4, 7 ∮ 2 = 7 + 8, 3 ∮ 5 = 3 + 4 + 5 + 6 + 7. According to this, we can calculate the value of 5 ∮ 8 and find the solution

5∮8=5+6+7+8+9+10+11+12=68

Direct method of permutation and combination There are four men and three women standing in a row to take pictures. There are only two women in line. How many kinds of arrangements are there?

First of all, select two of the three girls to form a whole. If the boys are arranged in full, there are 4! Kinds of permutations. There are 5 blanks in total, and then insert the girls in the space. Because there are 2 kinds of permutations in the whole formed by 2 girls, there are C (3, 2) x a (4, 4) x a (5, 2) x a (2, 2)!