1.   Find the missing number.

5, 10, 15, ___

    A. 20 B. 16
    C. 25 D. 30
    Hint

  2.   Find the missing number.

3, 6, 9, ___

    A. 10 B. 15
    C. 8 D. 12
    Hint

  3.   Find the missing number.

10, 20, 30, ___

    A. 35 B. 50
    C. 40 D. 25
    Hint

  4.   Find the missing number.

40, 50, 60, ___

    A. 65 B. 61
    C. 75 D. 70
    Hint

  5.   Find the missing number.

12, 15, 18, ___

    A. 25 B. 17
    C. 21 D. 19
    Hint