CBSE Class 4 General Knowledge Brain Teasers Worksheet Set 02

BRAIN TEASERS - 5

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 a decade = 10 years
Number of years in two and a half decades = \(2.5 \times 10 = 25\) years
Sum of chess pieces and octopus arms = \(32 + 8 = 40\)
Subtracting the years in two and a half decades = \(40 - 25 = 15\)
The answer is 15.
In simple words: Add 32 and 8 to get 40, then subtract 25 to get 15.

Exam Tip: Always break down multi-step word problems into individual mathematical operations to avoid calculation errors.

Question 2. A gardener dug a hole 2 meters wide, 3 metres long and 1 metre deep. How many handfuls of soil are there in the hole?
Answer: None. A hole is empty space where soil was removed from, so there is no soil inside the hole.
In simple words: By definition, a hole has nothing in it because the soil has already been dug out.

Exam Tip: Read trick questions carefully and pay attention to logical definitions rather than rushing into calculating volumes.

Question 3. Which is longer: \(4\frac{1}{2}\) feet or 54 inches?
Answer: 1 foot = 12 inches
\(4\frac{1}{2}\) feet = \(4.5 \times 12\) inches = 54 inches
Both lengths are equal.
In simple words: Convert feet into inches by multiplying by 12. Both measurements turn out to be 54 inches.

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: add two zeros and double
In simple words: Multiplying by 200 is the same as multiplying by 100 (adding two zeros) and then multiplying by 2 (doubling).

Exam Tip: Shortcut mental math rules help you solve multiplication problems quickly and accurately.

Question 5. What are the next two letters in this series? Z V R N [ ] [ ]
Answer: Let us look at the alphabetical positions backwards from Z (26):
Z = 26
V = 22 (minus 4 positions)
R = 18 (minus 4 positions)
N = 14 (minus 4 positions)
Continuing the pattern by subtracting 4 from the position of N (14 - 4 = 10), the 10th letter is J.
Subtracting 4 from 10 gives 6, and the 6th letter is F.
The next two letters are J and F.
In simple words: Each letter moves backward in the alphabet by skipping 3 letters at a time.

Exam Tip: Write down the alphabet with numbers when solving letter series to easily find the skip pattern.

Question 6. Complete each series:

a. 25, 125, 625, ........................
Answer: 3125
Step-by-step: Each number is multiplied by 5 to get the next number (\(625 \times 5 = 3125\)).
In simple words: Multiply each term by 5.

b. A,C,E,1,3,5 B,D,F,2,4,6 G,I,K,7,9,11 ........................
Answer: L,N,P,12,14,16
Step-by-step: The pattern follows groups of alternating letters and numbers: (A,C,E, 1,3,5), (B,D,F, 2,4,6), (G,I,K, 7,9,11). The next logical group starting with the next set of letters and numbers is (L,N,P, 12,14,16).
In simple words: The sequence alternates between sets of odd-positioned alphabet letters and consecutive odd/even numbers.

c.
Answer: The pattern shows geometric outer shapes containing smaller inner shapes that double in quantity from the first box to the second box.
In simple words: Count the inner shapes and double them in the next figure.

d.

Answer: The letter pairs in each grid invert their positions horizontally and vertically (swapping top and bottom rows, and reversing letters left to right).
In simple words: Flip the letter blocks upside down and backwards.
Exam Tip: For visual pattern problems, inspect rotations, reflections, and positional swapping carefully.

Please click the below link to access CBSE Class 4 General Knowledge Worksheets (12) - Brain Teasers