69+96, 99+66, 78+87, 77+88. How to calculate convenience? What is the relationship between two questions in each group?

The answer to each group of two questions is the same, and the connection is only the exchange of single digits, so the calculation can be in any form.

For example, I calculate in the second form. The first group is equivalent to the sum of 6 1 1 and 9 1 1, and the second group is equivalent to the sum of 7 1 1 and 81,all of which are equivalent to 60.

For the first two questions, 96 can be changed from 69 to 100, 69 to 65,100+65 =165; The second way is the same as the latter two, almost the same. From 87 to 78, it becomes 90, from 78 to 75, from 90 to 75 = 165. The two questions in each group have the same ten digits, and the numbers are exchanged, and the calculation results are the same.

The number consisting of 1, 5 1 and 7 10 is (75).

2. A number with 7 digits and 5 digits is (57).

3.( 10/0) One is 10. (10) Ten is 100. 35 one is (35).

There are (10) tens in100. 100 one is (100). There are (20) in 20.

5. A number, counted from the right, the first digit is (a), the second digit is (a), and the hundredth digit is the hundredth digit.

The unit of 6 and 68 is (8), which means (8) (1); The decimal digit is (6), which means (6) (10).

7 and 39 have (9) 1 and (3) 10, and 1 is (4) 10.

8. The largest single digit is (9), the largest two digits are (99), and the difference between them is (90).

9. Ten numbers, 50 followed by (60).

10, both addends are 30, and the sum is (60).

1 1, which is greater than 9 and less than 14 in singular: (1 1, 13).

The numbers of 12, 12 and 17 are (13, 14, 15, 16).

13, write four two-digit numbers with six digits, in descending order:

(46)>(36)>(26)>( 16)。

14.8, 10, 25, 62, 79 and 86, the number closest to 80 is (79), the minimum two digits are (10) and the maximum number is (86). There are (2) odd numbers and (4) even numbers.

15, two digits more than tens of digits, the largest is (79), and the smallest is (13).

16, ten digits are two digits more than single digits 1, the largest is (98), and the smallest is (10).

17, the sum of the number in the unit and the number in the tenth place is 9 in two digits, with the largest being (90) and the smallest being (18).