How many integers between 500 and 600 include the digit 9 only once?
(A) 21
(B) 20
(C) 19
(D) 18
(E) 17
9 only once
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- sanju09
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- selango
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500>100a+10b+10c<600
a cant be 9
b=9,the possible values are 590,591,592,593,594,595,596,597,598-9 integers.
c=9,the possible values are 509,519,529,539,549,559,569,579,589- 9 integers.
Total - 18 integers having digit as 9 only once
a cant be 9
b=9,the possible values are 590,591,592,593,594,595,596,597,598-9 integers.
c=9,the possible values are 509,519,529,539,549,559,569,579,589- 9 integers.
Total - 18 integers having digit as 9 only once
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18
but i used manaual method
90 ...to 98 ---9
89 ,79 ...to 9-----9
so 18
ok making eq is sure shot method but in this case....
manual method was shorter...
but i used manaual method
90 ...to 98 ---9
89 ,79 ...to 9-----9
so 18
ok making eq is sure shot method but in this case....
manual method was shorter...
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- sanju09
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wonderfulkvcpk wrote:Number should be of the form 59X or 5X9
if its 59X, X can be filled in 9 ways (0-8)
if its 5X9, X can be filled in 9 ways (0-8)
We need either of these 2 to happen. so 9+9 = 18
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- kvcpk
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Thank you!!sanju09 wrote:wonderfulkvcpk wrote:Number should be of the form 59X or 5X9
if its 59X, X can be filled in 9 ways (0-8)
if its 5X9, X can be filled in 9 ways (0-8)
We need either of these 2 to happen. so 9+9 = 18