Practice Questions: Alpha-Numeric Sequence Puzzle | Science Olympiad Class 6 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: (b) 2
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 ( followed by Q but not preceded by R)
• R X P Q ( followed by Q but not preceded by R)

There are two instances where P is followed by Q but not preceded by R. Therefore, the correct answer is B) 2.

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: (b) 5
Explanation: To find the number of L's in the odd places, let's identify the L's at odd positions in the sequence:

That is, positions: 1, 3, 5, 7, 9, 11, 13, 15, 17

Now check each:

• 1 → L 

• 3 → L 

• 5 → L 

• 7 → P

• 9 → P

• 11 → Q

• 13 → L 

• 15 → L

• 17 → P

Total L's at odd positions: 5

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) Zero
(d) Four
Ans: (c) Zero
Explanation: We are asked to count the number of 6's which meet both of the following conditions:

1. Immediately preceded by a multiple of 3 (i.e., 3, 6, 9, etc.)
2. Not immediately followed by any prime number (Prime numbers ≤ 10: 2, 3, 5, 7)

Let’s examine each 6 in the series:

• 1st 6 → Preceded by 9 (✓), followed by 3 (✗ prime) → Not valid

• 2nd 6 → Preceded by 2 (✗) → Not valid

• 3rd 6 → Preceded by 4 (✗) → Not valid

• 4th 6 → Preceded by 2 (✗) → Not valid

• 5th 6 → Preceded by 4 (✗) → Not valid

• 6th 6 → Preceded by 3 (✓), followed by 2 (✗ prime) → Not valid

• 7th 6 → Preceded by 2 (✗) → Not valid

• 8th 6 → Preceded by 7 (✗) → Not valid

None of the 6's satisfy both conditions.

Q8: David ranks seventeenth from the top in a class of fifty-eight. What will be his rank from the last?
(a) 41st
(b) 42nd
(c) 43rd
(d) 44th
Ans: (b) 42nd
Explanation: David ranks seventeenth from the top in a class of fifty-eight. To find his rank from the last, subtract his rank from the total number of students:
58 − 17 = 41
So, David's rank from the last is 41st. 

Therefore, David's rank from the last is 42nd, because:

• The student ranked 1st from the last is the 58th from the top.
• The student ranked 2nd from the last is the 57th from the top.
• Following this pattern, David (17th from top) is: 58 - 17 + 1 = 42

So, he is 42nd from the last.

Q9: If the day after tomorrow is Monday, then what day is it today?
(a) Saturday
(b) Sunday
(c) Monday
(d) Tuesday
Ans: (a) Saturday
Explanation: We are told:
The day after tomorrow is Monday.

Let’s work backward:

• Day after tomorrow = Monday

• So, Tomorrow = Sunday

• Therefore, Today = Saturday

Q10: Emily remembers that her friend's birthday was between the 8th and 11th of July, while her friend recalls being born after the 9th but before the 12th of July. If both statements are correct, on which date was Emily's friend born?
(a) 9th
(b) 10th
(c) 11th
(d) 9th or 10th
Ans: (b) 10th
Explanation: Combining the information, Emily's friend was born after the 9th but before the 12th of July. Since Emily remembers that her friend's birthday was between the 8th and 11th of July, the only date that satisfies both conditions is the 10th of July. Therefore, the correct answer is B) 10th.