Question

7. How many 6-digit numbers are there in all?
8. How many 7-digit numbers are there in all?
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Answer 1

there are lakhs of 6 and 7 digit numbera

Answer 2

Answer:

7) The smallest digit is 0 that cannot be used in the highest place value. So 1 which is the second smallest digit can be used in the highest place value.

The smallest six-digit number =100000

We know that the largest digit is 9 which can be used in any place

The largest six-digit number = 999999

IN terms of AP (Arithmetic progression)

a = 100000

Last term = 999999

Difference (d) = 1

The formula to calculate the nth term is

an = a + (n – 1)d

999999 = 100000 + (n – 1) × 1

899999 = n – 1

n = 900000

∴ there are 900,000 6-digit numbers in all.

8) The first 7 digit number is, 1000000

The last 7 digit number is 9999999

So, the number of 7 digit numbers is,

(9999999–1000000)+1=9000000.