Practice Questions: Number Sense | Math Olympiad for Class 5 PDF Download

A. Multiple Choice Questions (MCQs)

Q1: The smallest 7-digit number is:
Option A: 9,99,999
Option B: 10,00,000
Option C: 1,00,000
Option D: 99,99,999
Ans: 10,00,000
Solution: The smallest 7-digit number is one more than the largest 6-digit number (9,99,999). Hence, it is 10,00,000.

Q2: The largest 8-digit number is:
Option A: 10,00,00,000
Option B: 9,99,99,999
Option C: 1,00,00,000
Option D: 99,99,999
Ans: 9,99,99,999
Solution: The largest 8-digit number is all 9’s, i.e., 9,99,99,999.

Q3: What is the place value of 6 in 7,68,45,921?
Option A: 6,00,00,000
Option B: 60,00,000
Option C: 6,00,000
Option D: 600
Ans: 60,00,000
Solution: The digit 6 is in the ten lakh place. So, its place value = 6 × 10,00,000 = 60,00,000.

Q4: Face value of 7 in 4,37,29,108 is:
Option A: 7
Option B: 700
Option C: 70,000
Option D: 7,00,000
Ans: 7
Solution: Face value means the digit itself, so the face value of 7 = 7.

Q5: Which number is greater? 8,23,45,912 or 8,32,45,912
Option A: 8,23,45,912
Option B: 8,32,45,912
Option C: Both are equal
Option D: Cannot be compared
Ans: 8,32,45,912
Solution: Both numbers start with 8 in the crore place. Compare next digit: 2 (ten lakh) vs 3 (ten lakh). Since 3 > 2, the greater number is 8,32,45,912.

Q6: What is the successor of 59,99,999?
Option A: 59,99,998
Option B: 60,00,000
Option C: 59,00,000
Option D: 59,99,999
Ans: 60,00,000
Solution: Successor means the next number (+1). 59,99,999 + 1 = 60,00,000.

Q7: What is the predecessor of 1,00,00,000?
Option A: 9,99,999
Option B: 9,99,99,999
Option C: 99,99,999
Option D: 10,00,000
Ans: 99,99,999
Solution: Predecessor means the previous number (–1). So, 1,00,00,000 – 1 = 99,99,999.

Q8: 4,56,78,901 in words (Indian System) is:
Option A: Forty-five million six hundred seventy-eight thousand nine hundred one
Option B: Four crore fifty-six lakh seventy-eight thousand nine hundred one
Option C: Forty-five lakh six thousand seven hundred ninety-one
Option D: Four crore fifty-six thousand seven hundred eighty-nine
Ans: Four crore fifty-six lakh seventy-eight thousand nine hundred one
Solution: In the Indian system, 4,56,78,901 is read as four crore fifty-six lakh seventy-eight thousand nine hundred one.

Q9: In International system, 72,345,678 is read as:
Option A: Seventy-two crore thirty-four lakh five thousand six hundred seventy-eight
Option B: Seventy-two million three hundred forty-five thousand six hundred seventy-eight
Option C: Seven crore twenty-three lakh forty-five thousand six hundred seventy-eight
Option D: Seventy-two lakh thirty-four thousand five hundred sixty-seven
Ans: Seventy-two million three hundred forty-five thousand six hundred seventy-eight
Solution: In International system, digits are grouped in thousands and millions. So, 72,345,678 is seventy-two million three hundred forty-five thousand six hundred seventy-eight.

Q10: Which is the correct expanded form of 5,07,34,206?
Option A: 5,00,00,000 + 7,00,000 + 34,000 + 206
Option B: 50,00,000 + 7,00,000 + 30,000 + 4,000 + 200 + 6
Option C: 5,00,00,000 + 7,00,000 + 30,000 + 4,000 + 200 + 6
Option D: 5,00,000 + 7,00,000 + 34,000 + 200 + 6
Ans: 5,00,00,000 + 7,00,000 + 30,000 + 4,000 + 200 + 6
Solution: Write each digit according to its place value: 5 crore + 7 lakh + 30 thousand + 4 thousand + 200 + 6.

B. Fill in the Blanks

Q11: The smallest 8-digit number is __________.
Ans: 1,00,00,000
Solution: After the largest 7-digit number (99,99,999), the next number is 1,00,00,000, the smallest 8-digit number.

Q12: The place value of 4 in 6,43,27,198 is __________.
Ans: 40,00,000
Solution: 4 is in the ten lakh place, so place value = 4 × 10,00,000 = 40,00,000.

Q13: The face value of 9 in 9,87,65,432 is __________.
Ans: 9
Solution: Face value is always the digit itself.

Q14: The predecessor of 45,00,000 is __________.
Ans: 44,99,999
Solution: Predecessor = number – 1 → 45,00,000 – 1 = 44,99,999.

Q15: In Indian system, commas are placed after __________ digits, then every __________ digits.
Ans: 3 digits, then every 2 digits
Solution: The first comma is after 3 digits (hundreds place), then after every 2 digits (thousands, lakhs, crores).

C. Short Ans Questions

Q16: Write the number name of 3,40,56,789 in Indian system.
Ans: Three crore forty lakh fifty-six thousand seven hundred eighty-nine

Q17: Write the number name of 34,056,789 in International system.
Ans: Thirty-four million fifty-six thousand seven hundred eighty-nine

Q18: Compare 6,78,90,123 and 6,87,90,123. Which is greater?
Ans: 6,87,90,123
Solution: Compare crore → 6 = 6, compare ten lakh → 7 vs 8 → 8 is bigger. So, 6,87,90,123 is greater.

Q19: Write 7,08,05,010 in expanded form (Indian system).
Ans: 7,00,00,000 + 8,00,000 + 5,000 + 10
Solution: Each digit is written according to its place value.

Q20: Convert 5 crores into millions.
Ans: 50 million
Solution: 1 crore = 10 million. So, 5 crores = 5 × 10 = 50 million.