Elitmus
Exam
Numerical Ability
Permutation and Combination
how many 4 digit no can be made from 2,3,4,5,6,7 that divide by 25.
Read Solution (Total 9)
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- In order for a number to be divisible by 25, the number must end in 00, 25, 50, or 75.
No zero is in the list of options, so 00 or 50 cannot be possible.
25 and 75 are possible. So working backwards:
ones digit: must be a 5. Only 1 option.
tens digit: can be a 2 or 7. 2 options.
100s digit: can be any of the remaining 4 numbers left.
1000s digit: can be any of the remaining 3 numbers left.
So multiply each digit's "options" to get the answer:
1 * 2 * 4 * 3 = 24
- 10 years agoHelpfull: Yes(18) No(5)
- If repetition is allowed then d ans will be diff..
ones and tens digits are still the same at 1 and 2 respectively, since it still has to be divisible by 25.
But the other two digits can then be any of the 6 numbers.
So that gives us:
1 * 2 * 6 * 6 = 72 - 10 years agoHelpfull: Yes(13) No(3)
- at unit place only 5
nd 2nd place only 2,7
so total no. are
4*3*2*1=24 - 10 years agoHelpfull: Yes(2) No(3)
- how it can be 24 ....
calculate it by this way
For number which start with 2
2225,2275
2325,2375,
2425,2475
2525,2575
2625,2675
2725,2775
similarly for number which start with 3,4,5,6,7
so total number we got is 12*6=72 - 10 years agoHelpfull: Yes(2) No(0)
- numer will be divisible by 25 if we have 25 and 75 as last 2 digit
in this case
total number will be
if last 2 digit are 25 then= 6*6 way for first 2 digit
and if last 2 digit are 75 then=6*6 for first 2 digit
so total 36+36=72 number can be formed - 10 years agoHelpfull: Yes(1) No(1)
- since we need to fill 4 places the unit place filled by 5 that is 1way.then the rest in 5,4,3 ways.so ans is 60.
- 10 years agoHelpfull: Yes(0) No(4)
- to divide number by 25.......last 2 numbers must be 25 or 75
so they are fixed....
therefore,
No. of digits divisible by 25 are = 1*2*3*4 = 24 - 10 years agoHelpfull: Yes(0) No(1)
- ques ye tha how many four digit can be formed using 2,3,4,5,6,7 only once divisible by 25
a 12
b 20
c 24
d 40 - 10 years agoHelpfull: Yes(0) No(0)
- 4 digit no means
_ _ _ _ = ?
Solution- if the repetition is allowed then
_ _ 25 =?
we know that Total numbers are (i.e) 2, 3 , 4 , 5, 6 , 7 = 6
now we have to fill 2 digits of _ _ 24
So in this 1st disit 6 numbers can come and in the second digit also 6 numbers can come so 6 * 6 = 36
so in this way _ _ 24 = 36 numbers
like this way only
_ _ 75 = 6 * 6 = 36 numbers
so total 36+36 =72
But if the digits are not repeted then _ _ 25 = 1st digit can be of 4 numbers and 3 numbers so 4 * 3 =12
so total 12+ 12 = 24
:)
like this only _ _ 75 = 1st digit can be of 4 numbers
- 10 years agoHelpfull: Yes(0) No(0)
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