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Find the sum of all 3 digit natural numbers which contain at least one odd digit and at least one even digit

Find the sum of all 3 digit natural numbers which contain at least one  odd digit and at least one even digit


 

Grade:10

1 Answers

SAGAR SINGH - IIT DELHI
879 Points
11 years ago

Dear aritra,

If 1st digit is odd 50% of no.s can be there in last two places.
if it is odd rest 50% can be there.
till 1 to 8 in first place sum of last two=4*((101*100)/2)=4*5050=20200
if 9 rests at 1st place sum=5050/2=2525
so total=20200+2525=22725
but we have to add hundred's place. so sum of hundred's place is 50*(100+200+300+400+500+600+700+800+900)…
so sum=225000+22725=247725

 

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Sagar Singh

B.Tech, IIT Delhi

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