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d2: q3: The no of different 7 digit nos that can be written using only 3 digits 1,2&3 under the condition that the digit 2 occurs exactly twice in each no is?

d2: q3:


The no of different 7 digit nos that can be written using only 3 digits 1,2&3 under the condition that the digit 2 occurs exactly twice in each no is?

Grade:12

1 Answers

Badiuddin askIITians.ismu Expert
148 Points
14 years ago

Dear jee king

first select the 2 position out of 7 position and put 2 there =7C2 ways

and rest 5 position can be filled by 2 ways either by 1 or 3

so total ways

= 7C2 *2*2*2*2*2 =672 ways


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