CBSE Class 4 General Knowledge Brain Teasers Worksheet Set 04

Question 1. Add the number of chess pieces at the start of a game to the number of arms on an octopus and subtract the number of years in two and a half decades. What is the answer?
Answer: Number of chess pieces at the start of a game = 32
Number of arms on an octopus = 8
Number of years in one decade = 10 years
Number of years in two and a half decades = \(2.5 \times 10 = 25\)
Calculation = 32 + 8 - 25 = 40 - 25 = 15
In simple words: First add 32 and 8 to get 40, then subtract 25 to get 15.
Exam Tip: Always break down word problems with multiple steps into individual arithmetic operations carefully.

Question 2. A gardener dug a hole 2 metres wide, 3 metres long and 1 metre deep. How many handfuls of soil are there in the hole?
Answer: Volume of the hole = \(2 \text{ m} \times 3 \text{ m} \times 1 \text{ m} = 6 \text{ m}^3\)
Since the soil has been dug out of the hole, there is no soil left inside the hole. The hole is completely empty.
In simple words: A hole is empty space, so there is zero soil inside it.

Exam Tip: Read trick questions carefully; do not calculate volume when asked about the contents of an empty hole.

Question 3. Which is longer: \(4\frac{1}{2}\) feet or 54 inches?
Answer: We know that 1 foot = 12 inches.
Convert \(4\frac{1}{2}\) feet into inches: \(4.5 \times 12 = 54\) inches.
Both lengths are equal to 54 inches.
In simple words: Both measurements are exactly the same length.

Exam Tip: Always convert measurements to the same unit before comparing them.

Question 4. If you multiply any number by 200, all you have to do to get the correct answer is add .......................... and double
Answer: To multiply by 200, you can multiply by 2 and then multiply by 100 (which is the same as adding two zeros). Therefore, the missing word is "two zeros".
In simple words: Multiplying by 200 is the same as multiplying by 2 and annexing two zeros.

Exam Tip: Memorize shortcut rules for multiplying by powers and multiples of 10.

Question 5. What are the next two letters in this series? Z V R N [ ] [ ]
Answer: Let us look at the reverse alphabetical positions of the letters:
Z is position 26
V is position 22 (minus 4)
R is position 18 (minus 4)
N is position 14 (minus 4)
Next letter: 14 - 4 = 10, which is J
Following letter: 10 - 4 = 6, which is F
Answer: J, F
In simple words: Each letter moves backward in the alphabet by 4 positions.

Exam Tip: Write down the alphabet from A to Z with numbers to easily solve reverse sequence puzzles.

Question 6. Complete each series:
a. 25, 125, 625, ............
Answer: Each term is multiplied by 5 to get the next term.
\(25 \times 5 = 125\)
\(125 \times 5 = 625\)
\(625 \times 5 = 3125\)
Answer: 3125
In simple words: Multiply each number by 5 to find the next number.

Exam Tip: Check the ratio between consecutive numbers to identify geometric sequences.

Question 6.
b. A,C,E,1,3,5 B,D,F,2,4,6 G,I,K,7,9,11 ............
Answer: The pattern consists of groups of alternating letters and numbers: (A,C,E,1,3,5), (B,D,F,2,4,6), (G,I,K,7,9,11). Following the sequence of letter groups starting with C, D, E... and numbers, the next group is (H,J,L,8,10,12).
Answer: H,J,L,8,10,12
In simple words: Follow the alternating pattern of odd letters and numbers.

Exam Tip: Look for repeating blocks or alternating patterns in combined alphanumeric series.

Question 6.
c.
Answer: Looking at the numbers inside the circles, the first circle contains 5 and the second contains 25 (\(5^2 = 25\)). Following this squaring pattern, the next number is \(25^2 = 625\).
Answer: 625 inside a circle within a triangle
In simple words: Square the number in the previous circle to get the next number.

Exam Tip: Look for mathematical relationships such as squares or cubes between consecutive diagram figures.

Question 6.
d.

Answer: The matrices alternate columns and reverse alphabetical pairs between top and bottom rows. Following the alternating pattern of the first box, the fourth box mirrors the second box with swapped positions.
Answer:

In simple words: Rotate and invert the letter pairs in each grid box.
Exam Tip: Analyze spatial orientation and letter mirroring in matrix-based visual puzzles.