It is around 1.81 kilograms
The way you work this out is by thinking about the odds of each singular event, then finding the overall odds based on the individual odds.
The number of different books Mrs. Reid can choose is 9, so the first number is 9.
Mrs. Reid has picked one book so far, so now she has (1 - 9) = 8 books to choose from.
The of different books Mrs. Reid can choose now is 8, so your second number is 8.
Mrs. Reid has picked 2 book thus far, so now there are (2 - 9) = 7 books to choose from.
The of different books Mrs. Reid can choose now is 7, so your second number is
7.
To get the total number of different choices, multiply all the singular events together:
To find the number of terms in the arithmetic sequence, we need to use the formula
where

is the nth number,

is the first number, n is the number of terms and d is the difference of the two consecutive numbers.
7373 = 1313 + (n - 1)(303)
7373 = 1313 + 303n - 303
7373 = 1010 + 303n
7373 - 1010 = 303n
6363 = 303n
6363 ÷ 303 = n
n = 21
Therefore, there are 21 terms in the arithmetic sequence given.