ISEE Middle Level Mathematics Achievement Flashcards: Missing Terms In Sequences

What this deck covers

This deck focuses on Missing Terms In Sequences, giving you a quick way to review the definitions, rules, and examples that matter most for ISEE Middle Level Mathematics Achievement.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the missing term in the geometric sequence $81, 27, _, 3$?

Answer: $9$. The geometric sequence has a common ratio of $\frac{1}{3}$, so multiply $27$ by $\frac{1}{3}$ to find the missing term.

Flashcard 2: What is the missing term in the sequence $3, 6, 12, 24, _, 96$ (each term doubles)?

Answer: $48$. Each term doubles the previous, so multiply $24$ by $2$ to find the missing term.

Flashcard 3: What is the missing term in the alternating sequence $10, 7, 14, 11, _, 15$?

Answer: $18$. The alternating sequence interweaves two arithmetic progressions with common difference $4$, placing $18$ in the fifth position.

Flashcard 4: What is the missing term in the arithmetic sequence $0.3, 0.6, _, 1.2$?

Answer: $0.9$. The arithmetic sequence has a common difference of $0.3$, so add $0.3$ to $0.6$ to find the missing term.

Flashcard 5: What is the missing term in the geometric sequence $2, 6, _, 54$?

Answer: $18$. The geometric sequence has a common ratio of $3$, so multiply $6$ by $3$ to find the missing term.

Flashcard 6: What is the missing term in the sequence $1, 11, 21, _, 41$ (numbers ending in $1$ with step $10$)?

Answer: $31$. The arithmetic sequence has a common difference of $10$, so add $10$ to $21$ to find the missing term.

Flashcard 7: What is the missing term in the sequence $1, 8, 27, _, 125$ (perfect cubes)?

Answer: $64$. The sequence consists of consecutive perfect cubes, so the fourth term is $4^3$.

Flashcard 8: What is the missing term in the alternating sequence $1, -2, 3, -4, _, -6$?

Answer: $5$. The sequence alternates positive and negative signs with consecutive integers, so the fifth term is positive $5$.

Flashcard 9: What is the missing term in the sequence $1, 2, 4, 7, _, 16$ (add $1,2,3,\dots$)?

Answer: $11$. The sequence adds consecutive integers starting from $1$, so add $4$ to $7$ to find the missing term.

Flashcard 10: What is the missing term in the arithmetic sequence $20, 16, 12, _, 4$?

Answer: $8$. The arithmetic sequence has a common difference of $-4$, so subtract $4$ from $12$ to find the missing term.

Flashcard 11: What is the missing term in the sequence $2, 3, 5, 8, _, 21$ (each term is sum of previous two)?

Answer: $13$. Each term is the sum of the two preceding terms, so add $5$ and $8$ to find the missing term.

Flashcard 12: What is the missing term in the geometric sequence $5, _, 45, 135$?

Answer: $15$. The geometric sequence has a common ratio of $3$, so multiply $5$ by $3$ to find the missing term.

Flashcard 13: What is the missing term in the sequence $1, 4, 9, _, 25$ (perfect squares)?

Answer: $16$. The sequence consists of consecutive perfect squares, so the fourth term is $4^2$.

Flashcard 14: What is the missing term in the sequence $2, 5, 10, 17, _, 37$ (add consecutive odd numbers)?

Answer: $26$. The sequence adds consecutive odd numbers starting from $3$, so add $9$ to $17$ to find the missing term.

Flashcard 15: What is the missing term in the arithmetic sequence $-4, -1, _, 5, 8$?

Answer: $2$. The arithmetic sequence has a common difference of $3$, so add $3$ to $-1$ to find the missing term.

Flashcard 16: What is the missing term in the sequence $4, 9, 16, _, 36$ (squares starting at $2^2$)?

Answer: $25$. The sequence consists of squares of consecutive integers starting from $2$, so the fourth term is $5^2$.

Flashcard 17: What is the missing term in the arithmetic sequence $\frac{1}{2}, 1, _, 2$?

Answer: $\frac{3}{2}$. The arithmetic sequence has a common difference of $\frac{1}{2}$, so add $\frac{1}{2}$ to $1$ to find the missing term.

Flashcard 18: What is the missing term in the sequence $1, 3, 6, 10, _, 21$ (triangular numbers)?

Answer: $15$. The sequence consists of triangular numbers, so add $5$ to $10$ to find the missing term.

Flashcard 19: What is the missing term in the arithmetic sequence $3, 7, _, 15, 19$?

Answer: $11$. The arithmetic sequence has a common difference of $4$, so add $4$ to $7$ to find the missing term.

Flashcard 20: What is the missing term in the sequence $2, 6, 12, 20, _, 42$ (pronic numbers $n(n+1)$)?

Answer: $30$. The sequence consists of pronic numbers $n(n+1)$, so for $n=5$ the term is $5 \times 6$.

Flashcard 21: What is the missing term in the geometric sequence $\frac{1}{4}, _, 1, 2$?

Answer: $\frac{1}{2}$. The geometric sequence has a common ratio of $2$, so multiply $\frac{1}{4}$ by $2$ to find the missing term.

Flashcard 22: What is the missing term in the sequence $100, 50, 25, _, 6.25$ (each term halves)?

Answer: $12.5$. Each term is half the previous, so divide $25$ by $2$ to find the missing term.