Number System (Consolidating the Sense of Numberness)
ICSE Class 6 · Mathematics · Chapter 1
What this chapter covers
- Numbers up to five digits and beyond
- Comparing numbers
- Forming numbers from given digits
- Operations on large numbers
- Word problems on large numbers
Key points
- Every number is written with the ten digits 0 to 9.
- Each place is worth ten times the place on its right.
- After ten thousands come lakhs, ten lakhs and crores; one crore is the smallest eight-digit number.
- Put the first comma after three digits from the right, then after every two digits.
- The number with more digits is larger; with equal digits, compare from the left.
- Ascending order goes from smallest to largest; descending order goes from largest to smallest.
- For the smallest number from given digits, never put zero first.
- Check subtraction by adding, and check division by multiplying and adding the remainder.
- To change a larger unit of length or mass into a smaller unit, multiply.
Questions answered
Write "four lakh six thousand twenty-three" in figures.
4,06,023. The ten thousands and the hundreds are empty, so they get zeros.
In 3,52,846, what are the face value and the place value of the digit 5?
The face value is 5. The digit 5 sits in the ten thousands place, so its place value is 50,000.
Put the sign < or > between each pair: (a) 70,809 and 70,890; (b) 1,00,000 and 99,999. Then arrange 70,809; 7,08,090; 70,890 and 78,009 in ascending order.
(a) 70809 < 70890, because in the tens place 0 is less than 9. (b) 100000 > 99999, because 1,00,000 has more digits. In ascending order: 70,809; 70,890; 78,009; 7,08,090.
Form the largest and the smallest five-digit numbers using 6, 0, 3, 9 and 1, each once.
The largest is 96,310. The smallest is 10,369, because a number cannot begin with 0.
Change 6 km 45 m into metres and 9 kg 8 g into grams.
6,045 m and 9,008 g.
Subtract 2,87,459 from 5,06,000 and check your answer.
2,18,541. Check: 2,87,459 plus 2,18,541 is 5,06,000.
A shop sells 2,345 boxes of pencils. Each box holds 48 pencils. How many pencils does it sell?
2345 × 48 = 112560, so it sells 1,12,560 pencils.
Divide 76,543 by 12. What are the quotient and the remainder?
The quotient is 6,378 and the remainder is 7. Check: 12 × 6378 + 7 = 76543.