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JEE Advanced · Mathematics · 4. P&C

The number of 4-digit integers in the closed interval 2022,4482 formed by using the digits 0,2,3,4,6,7 is ______.

  1. A 569
  2. B 150
  3. C 846
  4. D 540
Verified Solution

Answer & Solution

Correct Answer

(A) 569

Step-by-step Solution

Detailed explanation

Given the number to be formed by using the digits 0,2,3,4,6,7 
Now assuming counting integers starting from 2
Case-I: if zero on 2nd place
(i) 2 0 2  _, now here at unit place 5 number can take place except zero {as 2020<2022}, so 5 possible way.
(ii) 2 0 _ _, now here at ten's place 4 number 3,4,6,7 can take place  and at unit place all 6 number can take place so total 4×6=24 possible way
Case-II: If non-zero number on 2nd place
i.e 2  _5  _6  _6, here at hundredth place 5 possibility will be there and at unit and ten's place 6 & 6 possibility will be there, so in total 5×6×6=180 possible cases,
Case -III when counting integers starting from 3
3_6_6_6 here total 6×6×6=216 possible cases
Case -IV when counting integers starting from 4
(i) If 0,2 or 3 on 2nd place
i.e., 4_3_6_6 here total 3×6×6=108 possible cases
(ii) If 4 on 2nd place
i.e., 34_6_6 here total 6×6=36 possible cases
So, total possible cases will be 5+24+180+216+108+36=569 numbers
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