99 multiplied by 9 is equal to 891. To calculate this, you would multiply the digit in the units place of the first number (9) by the second number (9) to get 81, and then multiply the digit in the tens place of the first number (9) by the second number (9) to get 810. Finally, you would add these two results together to get the final answer of 891.
99+sqt9xsqt9/9
Multiples of 9 are numbers that can be divided by 9 without leaving a remainder. They follow a pattern of increasing by 9 each time. The first few multiples of 9 are 9, 18, 27, 36, 45, and so on. In general, the multiples of 9 can be represented as 9n, where n is a positive integer.