Look carefully for the pattern, and then choose which pair of numbers comes next.

#### 28 25 5 21 18 5 14

Explanation: This is an alternating subtraction series with the interpolation of a random number, 5, as every third number. In the subtraction series, 3 is subtracted, then 4, then 3, and so on.

#### 8 11 21 15 18 21 22

Explanation: This is an alternating addition series, with a random number, 21, interpolated as every third number. The addition series alternates between adding 3 and adding 4. The number 21 appears after each number arrived at by adding 3.

#### 9 16 23 30 37 44 51

Explanation: Here is a simple addition series, which begins with 9 and adds 7.

#### 2 8 14 20 26 32 38

Explanation: This is a simple addition series, which begins with 2 and adds 6.

#### 9 11 33 13 15 33 17

Explanation: In this alternating repetition series, a random number, 33, is interpolated every third number into a simple addition series, in which each number increases by 2.

#### 2 3 4 5 6 4 8

Explanation: This is an alternating addition series with a random number, 4, interpolated as every third number. In the main series, 1 is added, then 2 is added, then 1, then 2, and so on.

#### 17 17 34 20 20 31 23

Explanation: This is an alternating subtraction series with repetition. There are two different patterns here. In the first, a number repeats itself; then 3 is added to that number to arrive at the next number, which also repeats. This gives the series 17, 17, 20, 20, 23, and so on. Every third number follows a second pattern, in which 3 is subtracted from each number to arrive at the next: 34, 31, 28.

#### 6 20 8 14 10 8 12

Explanation: This is an alternating addition and subtraction series. In the first pattern, 2 is added to each number to arrive at the next; in the alternate pattern, 6 is subtracted from each number to arrive at the next.

#### 21 25 18 29 33 18

Explanation: This is a simple addition series with a random number, 18, interpolated as every third number. In the series, 4 is added to each number except 18, to arrive at the next number.

#### 75 65 85 55 45 85 35

Explanation: This is a simple subtraction series in which a random number, 85, is interpolated as every third number. In the subtraction series, 10 is subtracted from each number to arrive at the next.