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Answer Key & Detailed Solutions
Q1. [1 Mark]
8,04,06,503
= Eight crore four lakh six thousand five hundred three
Q2. [1 Mark]
1 crore = 1,00,00,000
3 crores = 3,00,00,000
1 million = 10,00,000
3,00,00,000 ÷ 10,00,000 = 30 million
Q3. [1 Mark]
In 9,56,23,018 the digit 6 is in the ten-lakhs place.
Wait — let’s identify carefully:
9 | 56 | 23 | 018
9 = crores, 5 = ten-lakhs, 6 = lakhs, 2 = ten-thousands, 3 = thousands, 0 = hundreds, 1 = tens, 8 = ones
The 6 is in the lakhs place.
Place value of 6 = 6,00,000 (Six lakh)
Q4. [1 Mark]
5,03,50,427
First 5 (leftmost): crores place → place value = 5,00,00,000
Second 5: ten-thousands place → place value = 50,000
Difference = 5,00,00,000 − 50,000 = 4,99,50,000
= Four crore ninety-nine lakh fifty thousand
Q5. [1 Mark]
7,84,96,310
Ten-lakh digit: 4. Look at the next digit (lakh): 9.
Wait — to round to nearest ten lakh: 7,84,96,310. The ten-lakhs digit is 8. The lakhs digit is 4.
Since 4 < 5, round down.
Answer: 7,80,00,000
Q6. [1 Mark]
m = 4, n = 3
At most m + n = 4 + 3 = 7 digits
At least m + n − 1 = 4 + 3 − 1 = 6 digits
Verification: 1000 × 100 = 1,00,000 (6 digits) ✅; 9999 × 999 = 99,89,001 (7 digits) ✅
Q7. [2 Marks]
Let’s count the digits:
4,56,789 → 6 digits [1 mark for correct identification]
45,67,893 → 7 digits
4,56,78,930 → 8 digits
45,67,89,300 → 9 digits
Ascending order:
4,56,789 < 45,67,893 < 4,56,78,930 < 45,67,89,300 [1 mark]
Q8. [2 Marks]
(a) Six crore forty lakh three thousand seventy-five [1 mark]
= 6,00,00,000 + 40,00,000 + 3,000 + 75
= 6,40,03,075
(b) Nine hundred eight million fifty-two thousand four hundred [1 mark]
= 908,000,000 + 52,000 + 400
= 908,052,400
In Indian system: 90,80,52,400
Q9. [2 Marks]
3,56,789 = 3 × 1,00,000 + 5 × 10,000 + 6 × 1,000 + 7 × 100 + 8 × 10 + 9 × 1
But we only have +10000 as maximum. So:
+10000 pressed: 35 times (to get 3,50,000) [1 mark]
+1000 pressed: 6 times (to add 6,000)
+100 pressed: 7 times (to add 700)
+10 pressed: 8 times (to add 80)
+1 pressed: 9 times (to add 9)
Total = 35 + 6 + 7 + 8 + 9 = 65 clicks [1 mark]
Q10. [2 Marks]
(a) 372 × 50 [1 mark]
Trick: 50 = 100 ÷ 2
372 × 100 = 37,200
37,200 ÷ 2 = 18,600
(b) 456 × 125 [1 mark]
Trick: 125 = 1000 ÷ 8
456 × 1000 = 4,56,000
4,56,000 ÷ 8 = 57,000
Q11. [2 Marks]
Increase = 31,20,450 − 23,45,678 [1 mark]
= 7,74,772
In words: Seven lakh seventy-four thousand seven hundred seventy-two [1 mark]
Q12. [3 Marks]
Digits: 0, 1, 2, 4, 7, 9
(a) Largest 6-digit number: [1 mark]
Arrange in descending order: 9,74,210
(b) Smallest 6-digit number: [1 mark]
First digit cannot be 0. Use 1 (smallest non-zero).
Remaining in ascending: 0, 2, 4, 7, 9
Answer: 1,02,479
(c) Difference: [1 mark]
9,74,210 − 1,02,479 = 8,71,731
= Eight lakh seventy-one thousand seven hundred thirty-one
Q13. [3 Marks]
(a) Monthly supply: [1 mark]
25,750 × 30 = 7,72,500 litres
(b) Monthly revenue: [1 mark]
7,72,500 × 54
= 7,72,500 × 50 + 7,72,500 × 4
= 3,86,25,000 + 30,90,000
= ₹4,17,15,000
(c) In International system: [1 mark]
4,17,15,000 = 41,715,000
= Forty-one million seven hundred fifteen thousand
Q14. [3 Marks]
Condition 1: Rounded to nearest thousand = 47,000 [1 mark]
This means: 46,500 ≤ N ≤ 47,499
Condition 2: Rounded to nearest hundred = 46,800 [1 mark]
This means: 46,750 ≤ N ≤ 46,849
Intersection: [1 mark]
max(46,500, 46,750) ≤ N ≤ min(47,499, 46,849)
46,750 ≤ N ≤ 46,849
Count = 46,849 − 46,750 + 1 = 100 numbers
Q15. [3 Marks]
(a) India ÷ Sri Lanka: [1 mark]
32,87,263 ÷ 65,610 ≈ 33,00,000 ÷ 66,000 = 50
India’s area is approximately 50 times Sri Lanka’s area.
(b) Total area: [1 mark]
32,87,263 + 8,81,913 + 1,47,570 + 65,610 = 43,82,356 sq km
In International: 4,382,356
= Four million three hundred eighty-two thousand three hundred fifty-six sq km
(c) India rounded to nearest lakh: [1 mark]
32,87,263 → ten-thousands digit is 8 (≥ 5), round up.
Answer: 33,00,000 (Thirty-three lakh)
Q16. [4 Marks]
(a) Cars per year: [1 mark]
450 × 25 × 12 = 450 × 300 = 1,35,000 cars
(b) Total value: [1 mark]
1,35,000 × 8,75,000
= 1,35,000 × 8,75,000
= 1,181,25,00,000 → Wait, let me compute carefully:
135 × 875 = 1,18,125
So 1,35,000 × 8,75,000 = 1,18,125 × 105 × 103 ÷ 103
= 1,35,000 × 8,75,000 = 11,81,25,00,000
= ₹1,181.25 crore (approximately ₹1,181 crore)
(c) 15% increase: [1 mark]
Extra daily = 450 × 15/100 = 67.5 ≈ 68 extra cars/day
(d) Will it cross 2 lakh? [1 mark]
New daily = 450 + 68 = 518 cars
New yearly = 518 × 300 = 1,55,400
1,55,400 < 2,00,000 → No, it will NOT cross 2 lakh cars.
Q17. [4 Marks]
(a) Passengers per year: [1 mark]
2,30,00,000 × 365 = 83,95,00,00,000 ≈ 839.5 crore
≈ 840 crore passengers per year
(b) Daily revenue: [1 mark]
2,30,00,000 × 125 = 287,50,00,000
= ₹287.5 crore per day
(= ₹2,87,50,00,000)
(c) In International system: [1 mark]
2,87,50,00,000 = 2,875,000,000
= Two billion eight hundred seventy-five million
(d) Percentage increase: [1 mark]
Target: 1,000 crore = 10,00,00,00,000 per year
Required daily = 10,00,00,00,000 ÷ 365 ≈ 2,73,97,260 per day
Current daily = 2,30,00,000
Increase needed = 2,73,97,260 − 2,30,00,000 = 43,97,260
Percentage = (43,97,260 / 2,30,00,000) × 100 ≈ 19.1% increase
Q18. Bonus [4 Marks]
Let the 7-digit number be: _ _ _ _ _ _ _
Positions: TL L TTh Th H T O (Ten-Lakhs, Lakhs, Ten-Thousands, Thousands, Hundreds, Tens, Ones)
Given: [1 mark each clue]
• Ten-lakhs = 7
• Thousands = 4, Tens = 4
• Hundreds = 2
• Ten-thousands = 2 × Hundreds = 2 × 2 = 4
• Lakhs = Ones + 3
• Sum of all digits = 30
Known digits: 7, L, 4, 4, 2, 4, O
Sum: 7 + L + 4 + 4 + 2 + 4 + O = 30
21 + L + O = 30
L + O = 9
Also, L = O + 3
So: (O + 3) + O = 9 → 2O = 6 → O = 3
L = 3 + 3 = 6
The number is: 76,44,243
= Seventy-six lakh forty-four thousand two hundred forty-three