A number more than 1200 and less than 1300 is such that all its digits except one digit are factor of 9.

What is the probability that number is more than 1250 ?

+1 vote

A number more than 1200 and less than 1300 is such that all its digits except one digit are factor of 9.

What is the probability that number is more than 1250 ?

+3 votes

Best answer

Let x be the number

If 1200 < x < 1300

Then thousands digit will be 1

Hundreds digit will be 2

Tens digit has 3 choices 1, 3, 9

Units digit has 3 choice 1, 3, 9

Total four digit numbers = 1*1*3*3 = 9

If 1250 < x then

Thousands digit will be 1

Hundreds digit will be 2

Tens digit will be 9

Units digit has 3 choice = 1, 3, 9

Total four digit numbers = 1*1*1*3 = 3

Probability = 3/9 = 1/3

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