The sum of the reciprocal of two consecutive natural numbers is 17 / 72. What are the two numbers?

The sum of the reciprocal of two consecutive natural numbers is 17 / 72. What are the two numbers?

17/72=(8+9)/(8*9)=1/8+1/9
So these two consecutive natural numbers are 8 and 9

A natural number, the sum of its digits is equal to 22, what is the minimum number

Because we want to be the smallest, we should reduce the number of digits as much as possible
To reduce the number of digits, we need to use the largest number in the lower order,
Fill in the numbers in the order of individual, ten and hundred
So the number of 9, 9, and 18, and the number of 100 only need to fill in 4
The answer is 499

For a natural number, the sum of its digits is equal to 25. What is the minimum number?

799

For a natural number, the sum of its digits is equal to 23. What is the minimum number?
emergency

Because it should be as small as possible, it's better to use three digits (not two digits, 9 + 9 = 18 < 23)
First, add up the two largest single digits: 9 + 9 = 18
Then calculate how many more: 23-18 = 5
Take the smallest number as a hundred and put two nines after it: 599