Practice Questions: Alpha-Numeric Sequence Puzzle | Math Olympiad for Class 5 PDF Download

• C L (immediately preceded by C)
• C L (immediately preceded by C)
• C L (immediately preceded by C)

So, there are three instances where the letter L is immediately preceded by the letter C. Therefore, the correct answer is C) Three.

Q2: How many P's are there in the following series which are followed by Q but not preceded by R?X P Q R P Q R P Q R X P Q R
(a) 1
(b) 2
(c) 3
(d) 4
Ans: (a) 1
Explanation: To find the number of P's that are followed by Q but not preceded by R, let's analyze the sequence:

• X P Q R (not followed by Q)
• P Q R P (not followed by Q)
• R X P Q (not followed by Q)

So far, there are no instances where P is followed by Q but not preceded by R. However, in the fourth occurrence:

• X P Q R (followed by Q, not preceded by R)

There is one instance where P is followed by Q but not preceded by R. Therefore, the correct answer is A) 1.

Q3: How many G's are there in the following sequence which are followed by H but not preceded by F?
R G F H G H F G H G R G H F G H
(a) 1
(b) 2
(c) 3
(d) 4
Ans: (b) 2
Explanation: To find the number of G's that are followed by H but not preceded by F, let's carefully analyze the sequence:

• R G F H (not followed by H)
• G H F G (followed by H, not preceded by F)
• H G R G (followed by H, not preceded by F)
• G H F G (followed by H, not preceded by F)

There are two instances where G is followed by H but not preceded by F. Therefore, the correct answer is B) 2.

Q4: How many L's are there in the odd places in the following sequence?
L Q L P L Q P L P L Q Q L P L Q P L
(a) 4
(b) 5
(c) 6
(d) 7
Ans: (a) 4
Explanation: To find the number of L's in the odd places, let's identify the L's at odd positions in the sequence:

• L Q L P (Odd position)
• L Q P L (Odd position)
• P L Q Q (Odd position)
• L Q P L (Odd position)

There are four instances where L is at an odd position in the sequence. Therefore, the correct answer is A) 4.

Q5: In the following series, how many such numbers are there which are divisible by 4 or 6 and immediately followed by a vowel?
L, 24, H, 18, 36, A, 42, 16, 25, 27, 48, E, 50, 49, 8
(a) Zero
(b) One
(c) Two
(d) Three
Ans: (c) Two
Explanation: To find the numbers that are divisible by 4 or 6 and immediately followed by a vowel, let's examine the given series:

• L, 24 (Divisible by 4, not followed by a vowel)
• H, 18 (Divisible by 6, not followed by a vowel)
• 36, A (Divisible by 4, followed by a vowel)
• 42, 16 (Divisible by 6, not followed by a vowel)
• 25, 27 (Not divisible by 4 or 6)
• 48, E (Divisible by 4, followed by a vowel)
• 50, 49 (Divisible by 4, not followed by a vowel)
• 8 (Divisible by 4, not followed by a vowel)

There are two instances where a number is divisible by 4 or 6 and immediately followed by a vowel. Therefore, the correct answer is C) Two.

Q6: How many such letters are there, each of which is followed by a digit divisible by 3, in the following series?
1 2 C 6 9 D 3 5 A 2 8 7 G 9 4 F 6
(a) 1
(b) 2
(c) 3
(d) 4
Ans: (d) 4
Explanation: To find the letters that are followed by a digit divisible by 3, let's examine the given series:

• 1 2 C (Followed by 6, which is divisible by 3)
• 6 9 D (Followed by 3, which is divisible by 3)
• 3 5 A (Followed by 2, which is not divisible by 3)
• 8 7 G (Followed by 9, which is divisible by 3)
• 9 4 F (Followed by 6, which is divisible by 3)

There are four instances where a letter is followed by a digit divisible by 3. Therefore, the correct answer is D) 4.

Q7: How many 6's are there in the following number series, each of which is immediately preceded by a multiple of 3 but not immediately followed by any prime number?
9 6 3 2 6 8 4 6 7 5 2 6 1 4 6 9 3 6 2 6 8 5 7 6 4
(a) One
(b) Two
(c) Three
(d) Four
Ans: (c) Three
Explanation: To find the 6's that are immediately preceded by a multiple of 3 but not immediately followed by any prime number, let's analyze the given series: