how many four digits numbers are formed such that the digits are in decreasing order

• START with 3 = 3_ _ _. You can fill in with digits 0,1,2. Hence 3C3 = 1
  START with 4 = 4_ _ _. (0,1,2,3). hence 4C3= 4
  START with 5, you have (0,1,2,3,4) to fill in the blanks behind 5, hence 5C3 = 10
  START with 6, 6C3=20
  7... = 7C3 = 35
  8...=8C3 = 56
  9...= 9C3 = 84
  so ans=1+4+10+20+35+56+84=210
• 9 years agoHelpfull: Yes(42) No(16)
• There are 10 digits from 0 to 9.
  Selecting 4 digits and they can be arranged in descending order only in 1 way
  Total number of ways = 10c4 = 210.
• 9 years agoHelpfull: Yes(30) No(1)
• when we make four digits no starting with 9,we get as
  9876,9765,9654,9543,9432,9321,9210.
  total seven digit we got
  lly for the digits stating from 8,7,6,5,4,3.we get 6,5,4,3,2,1.so total no is=7+6+5+4+3+2+1=28
• 9 years agoHelpfull: Yes(6) No(9)
• starts with 1=0
  starts with 2=0
  starts with 3=1 which is 3210
  starts with 4=2 which are 4321,4210 same way
  starts with 5=3 6=4 7=5 8=6 9=7 total=28
  same as gautam gaurav
• 9 years agoHelpfull: Yes(5) No(5)
• start with 987_ u can fill fill total 7 digit(0,1,2,3,4,5,6);;
  start with 986- u can fill total 6 digit(0,1,2,3,4,5);;;
  start with 985_ ;;;;;;;;;;;;;;;;;5 digit(0,1,2,3,4)simlarlly next then next
  start with 976-;;;;;;;;;;;;;;;;;;;;;;;;;;6 digit
  start with 975-;;;;;;;;;;;;;;;;;;;;;;;;;;5 digit and so on u got 84 when u fixed 9,,, 9c3=84,,,then next fixed 8 and find 8c3;
  slly 9c3+8c3+7c3+6c3+5c3+4c3+3c3=210
• 9 years agoHelpfull: Yes(5) No(1)
• ans:126
  let us consider the digit
  1 2 3 4 5 6 7 8 9
  four digit numbers are formed so that
  9C4= 9 8 7 6/4 3 2 1
  =126
• 9 years agoHelpfull: Yes(3) No(8)
• Decreasing order lowest 3210
  Decreasing order highest 9876
  Therefore, In 1st digit---->(3 to 9) =7 numbers
  In 2nd digit---->(2 to 8) =7 numbers
  In 3rd digit---->(1 to 7) =7 numbers
  In 4th digit---->(0 to 6) =7 numbers
  Therefore,four digits numbers are formed such that the digits are in decreasing order =(7+7+7+7)=28 (ans.)
  
  
  
  
  
• 9 years agoHelpfull: Yes(2) No(0)
• @ venkat ur ans is in proper way
  
• 9 years agoHelpfull: Yes(2) No(0)
• Decreasing order lowest 3210
  Decreasing order highest 9876
  Therefore, In 1st digit---->(3 to 9) =7 numbers
  In 2nd digit---->(2 to 8) =7 numbers
  In 3rd digit---->(1 to 7) =7 numbers
  In 4th digit---->(0 to 6) =7 numbers
  Therefore,four digits numbers are formed such that the digits are in decreasing order =(7*7*7*7)= 2401(ans)
  
• 9 years agoHelpfull: Yes(2) No(1)
• would like to clear the digits of the number should be in decreasing order, i.e. 3210, 4321, 4210, etc.
  
  Now coming back to ques.
  the smallest 4 digit number we see which can be formed by arranging the digits in descending order is 3210.
  for staring with 3 we have : 3210
  for staring with 4 we have : 4321, 4210
  for staring with 5 we have : 5432, 5321, 5210
  for staring with 6 we have : 6543, 6432, 6321, 6210
  similarly we come an conclusion that there are 28 such numbers that can be formed , i.e. 1+2+3+4+5+6+7=28.
  
  Some used combination to calculate the numbers but u all r getting it wrong when the DECREASING ORDER term comes into existence. And if u think m wrong then tell me any 4 numbers of 4 digits starting with 4 whose digits are arranged in decreasing order as few gave ans using combination like 4C3=4.
• 9 years agoHelpfull: Yes(1) No(0)
• START with 3 = 3_ _ _. You can fill in with digits 0,1,2. Hence 3C3 = 1
  START with 4 = 4_ _ _. (0,1,2,3). hence 4C3= 4
  START with 5, you have (0,1,2,3,4) to fill in the blanks behind 5, hence 5C3 = 10
  START with 6, 6C3=20
  7... = 7C3 = 35
  8...=8C3 = 56
  9...= 9C3 = 84
  so ans=1+4+10+20+35+56+84=210
• 9 years agoHelpfull: Yes(1) No(0)
• 126
  the numbers are
  123456789
  the solution is 9c4 = 9.8.7.6/4.3.2.1=126
  
• 9 years agoHelpfull: Yes(0) No(2)
• Well I don't exactly know the answer but one thing to be noticed here is that the digits of a number has to be in a decreasing order
• 9 years agoHelpfull: Yes(0) No(3)
• Start with 987_ , we have 9876,9875,9874...9870 = 7 possible outcomes.
  Next we use 986_, we get 6 outcomes.
  In this way we compute 98_ _, and we get 28 outcomes in total.
  Then we compute 9*** & finally **** in similar fashion.
  In the end we add all possible outcomes to get 179.
• 9 years agoHelpfull: Yes(0) No(2)
• @ krithika pls give the solution
• 9 years agoHelpfull: Yes(0) No(0)
• i think 28 is the correct answer
  
• 9 years agoHelpfull: Yes(0) No(0)