16. 4
6
8
10

```Answer

Answer: Option  D Explanation:In each star diagram, the number in the centre equals the sum of the top three numbers,
subtracting the sum of the bottom two numbers. ```

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17. 21
23
25
27

```Answer

Answer: Option  B Explanation:Starting top left, and moving down in columns from left to right, the numbers follow the sequence of
prime numbers from 2 to 23. ```

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18. 10
12
14
16

```Answer

Answer: Option  A Explanation:Numbers in the segments of the left hand circle equal the difference between numbers in corresponding
segments of the two right hand circles. ```

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19. 1133
1143
1153
1163

```Answer

Answer: Option  B Explanation:Starting with the top 3 digit number, the first digit increases by 2 as you descend, from 1 to 11.
The middle digit decreases by 1 each time, and the right hand digit alternates between 5 and 3. ```

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20. 4
5
6
7

```Answer

Answer: Option  C Explanation:Numbers in the lower left circle equal the sum of the numbers in corresponding segments of
the top two circles, and numbers in the lower right circle equal the difference of the
numbers in corresponding segments of the top two circles. ```

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