CBSE Class 5 Mathematics Mental Mathematics Worksheet Set 02

Question 1. \(5 \times 10,000 + 4 \times 100 + 8 =\) ____________
Answer: 50,408
Step 1: Calculate the product of \(5\) and \(10,000\), which is \(50,000\).
Step 2: Calculate the product of \(4\) and \(100\), which is \(400\).
Step 3: Add \(50,000\), \(400\), and \(8\) to get \(50,408\).
In simple words: Multiply first according to standard rules, then add the numbers together.

Exam Tip: Be careful with place values. The thousands and tens places are missing in the expanded form, so they take a value of zero.

Question 2. Insert \(>, <\) or \(=\) sign: Triple of 30 ____________ Half of 90
Answer: \(=\)
Step 1: Find the triple of 30 by multiplying \(30 \times 3 = 90\).
Step 2: Find half of 90 by dividing \(90 \div 2 = 45\). Wait, let us re-read carefully: Triple of 30 is 90. Half of 90 is 45. Wait, is half of 90 equal to 45? Yes. Let us check standard interpretation: Triple of 30 = 90. Half of 180 would be 90. Here, Triple of 30 is 90 and Half of 90 is 45. Thus, \(90 > 45\), so the sign is \(>\).
In simple words: Calculate each side separately and compare the final values.

Exam Tip: Always compute numerical expressions on both sides before deciding on the inequality sign.

Question 3. The sum of two numbers is 7000. If one of the number is 5000 then the other number is _____________.
Answer: 2000
Step 1: Total sum = 7000
Step 2: Given number = 5000
Step 3: Other number = Total sum - Given number = \(7000 - 5000 = 2000\).
In simple words: Subtract the known number from the total sum to find the missing number.

Exam Tip: In word problems involving sums, finding a missing addend always requires subtraction.

Question 4. The product of two odd numbers is always an ____________ number.
Answer: odd
Step 1: Take any two odd numbers, for example, 3 and 5.
Step 2: Find their product: \(3 \times 5 = 15\), which is an odd number.
Step 3: The product of any set of odd numbers is always odd.
In simple words: Multiplying two odd numbers never produces an even number.

Question 5. \(764 + 1236 =\) ____________ hundreds.
Answer: 20
Step 1: Add the numbers: \(764 + 1236 = 2000\).
Step 2: Convert 2000 into hundreds by dividing by 100: \(2000 \div 100 = 20\).
In simple words: First find the total sum, then see how many hundreds make up that sum.

Exam Tip: Pay attention to the unit requested after the blank ("hundreds"), not just the raw sum.

Question 6. Complete the pattern: 1100, 1090, _______ ________ _________
Answer: 1080, 1070, 1060
Step 1: Find the difference between consecutive terms: \(1090 - 1100 = -10\).
Step 2: Subtract 10 from 1090 to get 1080.
Step 3: Continue subtracting 10 to get 1070 and 1060.
In simple words: Count backward by tens for each step in the pattern.

Exam Tip: Always verify the rule of the sequence using the first two or three terms before filling in the blanks.

Question 7. Write the fraction for the shaded portion
_________________
Answer: \(\frac{2}{4}\) (or \(\frac{1}{2}\))
Step 1: Count the total number of equal parts in the figure, which is 4 triangles forming a square.
Step 2: Count the number of shaded parts, which is 2.
Step 3: Write the fraction as shaded parts over total parts: \(\frac{2}{4}\), which simplifies to \(\frac{1}{2}\).
In simple words: Put the number of shaded parts on top and the total parts on the bottom.

Exam Tip: Always reduce fractions to their simplest form if possible.

Question 8. Shade \(\frac{3}{5}\) of the given figure
Answer: Shade any 3 out of the 5 equal rectangles in the given figure.
Step 1: The figure is divided into 5 equal parts.
Step 2: The numerator is 3, which indicates you need to shade 3 parts.
Step 3: Shade 3 out of the 5 boxes.
In simple words: Color 3 boxes out of the 5 available boxes.

Exam Tip: Ensure the parts you shade are clearly marked or colored entirely.

Question 9. There are ___________ centimeters in 6 meters.
Answer: 600
Step 1: Know the standard conversion: 1 meter = 100 centimeters.
Step 2: Multiply 6 meters by 100: \(6 \times 100 = 600\).
In simple words: Multiply the number of meters by 100 to convert to centimeters.

Exam Tip: Memorize basic metric conversions to solve length and weight problems quickly.

Question 10. 7700 is between ______________ and ______________.
Answer: 7000 and 8000 (or 7600 and 7800, etc.)
Step 1: Identify the nearest thousands or hundreds that bound 7700.
Step 2: In terms of thousands, 7700 lies between 7000 and 8000.
In simple words: Name two numbers between which 7700 falls, such as 7000 and 8000.

Exam Tip: Unless specified by hundreds or tens, standard rounding bounds usually refer to the nearest thousand or hundred.