Missing Number in Sequences - ISEE Lower Level Mathematics Achievement

1. What is the missing term in the arithmetic sequence $\frac{1}{2}, \frac{3}{2}, \square, \frac{7}{2}$?

   $\frac{5}{2}$. The common difference is $1$, determined from $\frac{3}{2} - \frac{1}{2}$, and added to $\frac{3}{2}$ to find the missing term.

2. What is the missing term in the arithmetic sequence $\frac{5}{4}, \frac{3}{4}, \square, -\frac{1}{4}$?

   $\frac{1}{4}$. The common difference is $-\frac{1}{2}$, determined from $\frac{3}{4} - \frac{5}{4}$, and added to $\frac{3}{4}$ to find the missing term.

3. What is the missing term in the arithmetic sequence $1, 4, 7, \square$?

   $10$. The common difference is $3$, determined from $4 - 1$, and added to $7$ to find the missing term.

4. What is the missing term in the arithmetic sequence $-3, \square, 5, 9$?

   $1$. The common difference is $4$, determined from $9 - 5$, and subtracted from $5$ to find the missing term.

5. What is the missing term in the arithmetic sequence $8, 3, \square, -7$?

   $-2$. The common difference is $-5$, determined from $3 - 8$, and added to $3$ to find the missing term.

6. What is the missing term in the arithmetic sequence $30, 24, \square, 12$?

   $18$. The common difference is $-6$, determined from $24 - 30$, and added to $24$ to find the missing term.

7. What is the missing term in the arithmetic sequence $-10, -6, -2, \square$?

   $2$. The common difference is $4$, determined from $-6 - (-10)$, and added to $-2$ to find the missing term.

8. What is the missing term in the arithmetic sequence $3, 8, \square, 18$?

   $13$. The common difference is $5$, determined from $8 - 3$, and added to $8$ to find the missing term.

9. What is the missing term in the arithmetic sequence $9, 6, 3, \square$?

   $0$. The common difference is $-3$, determined from $6 - 9$, and added to $3$ to find the missing term.

10. What is the missing term in the arithmetic sequence $\square, -1, 2, 5$?

    $-4$. The common difference is $3$, determined from $2 - (-1)$, and subtracted from $-1$ to find the missing term.

11. What is the missing term in the arithmetic sequence $12, 9, 6, \square$?

    $3$. The common difference is $-3$, determined from $9 - 12$, and added to $6$ to find the missing term.

12. What is the common difference $d$ in the arithmetic sequence $7, 11, 15, \dots$?

    $d=4$. The common difference $d$ is found by subtracting the first term from the second, yielding $11 - 7 = 4$, consistent with $15 - 11 = 4$.

13. What is the missing term in the arithmetic sequence $\square, 14, 18, 22$?

    $10$. The common difference is $4$, determined from $18 - 14$, and subtracted from $14$ to find the missing term.

14. What is the missing term in the arithmetic sequence $\frac{2}{3}, \square, \frac{8}{3}, \frac{11}{3}$?

    $\frac{5}{3}$. The common difference is $1$, determined from $\frac{11}{3} - \frac{8}{3}$, and subtracted from $\frac{8}{3}$ to find the missing term.

15. What is the missing term in the arithmetic sequence $100, 90, \square, 70$?

    $80$. The common difference is $-10$, determined from $90 - 100$, and added to $90$ to find the missing term.

16. What is the missing term in the arithmetic sequence $4, \square, 10, 13$?

    $7$. The common difference is $3$, determined from $13 - 10$, and subtracted from $10$ to find the missing term.

17. What is the missing term in the arithmetic sequence $2.5, 3.0, \square, 4.0$?

    $3.5$. The common difference is $0.5$, determined from $3.0 - 2.5$, and added to $3.0$ to find the missing term.

18. What is the missing term in the arithmetic sequence $-2, 1, \square, 7$?

    $4$. The common difference is $3$, determined from $1 - (-2)$, and added to $1$ to find the missing term.

19. What is the missing term in the arithmetic sequence $6, \square, 16, 21$?

    $11$. The common difference is $5$, determined from $21 - 16$, and subtracted from $16$ to find the missing term.

20. What is the missing term in the arithmetic sequence $20, \square, 10, 5$?

    $15$. The common difference is $-5$, determined from $10 - 15$ or $5 - 10$, and added to $20$ to find the missing term.

21. What is the missing term in the arithmetic sequence $-1.2, -0.7, \square, 0.3$?

    $-0.2$. The common difference is $0.5$, determined from $-0.7 - (-1.2)$, and added to $-0.7$ to find the missing term.

22. What is the missing term in the arithmetic sequence $5, 2, \square, -4$?

    $-1$. The common difference is $-3$, determined from $2 - 5$, and added to $2$ to find the missing term.

23. What is the missing term in the arithmetic sequence $2, 2.8, \square, 4.4$?

    $3.6$. The common difference is $0.8$, determined from $2.8 - 2$, and added to $2.8$ to find the missing term.

24. What is the missing term in the arithmetic sequence $15, \square, 5, 0$?

    $10$. The common difference is $-5$, determined from $5 - 10$ or $0 - 5$, and added to $15$ to find the missing term.

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