1. Fill in the missing numbers in each a) \( 845 ; 865 ; 885 ; \)

To find the missing number in the sequence \( 845 ; 865 ; 885 ; \), we first observe the pattern in the numbers provided. 1. The first number is \( 845 \). 2. The second number is \( 865 \). 3. The third number is \( 885 \). Next, we calculate the difference between consecutive numbers: - The difference between \( 865 \) and \( 845 \) is: \[ 865 - 845 = 20 \] - The difference between \( 885 \) and \( 865 \) is: \[ 885 - 865 = 20 \] Since the difference is consistent at \( 20 \), we can conclude that this is an arithmetic sequence where each term increases by \( 20 \). To find the next number after \( 885 \), we add \( 20 \) to \( 885 \): \[ 885 + 20 = 905 \] Thus, the complete sequence is: \[ 845 ; 865 ; 885 ; 905 \] The missing number is \( 905 \).