Question { Persistent, 40912 }

if a number is choosen between 100 and 999 includeing these
numberrs what is the provbabilty that the number selected
does not contain a 7 is

Answer

total numbers from 100 to 999 = 900

total no of 7's
700 - 799 = 100

70-79 in all 100's except seventh hundred = 90

07,17,27...67,87,97 in
all 100's except seventh hundred = 90

total - 280
probability = (900-280)/900
= 31/45

Question { Deshaw, 20708 }

DESHAW placement papers --------- placement paper 4

Answer

Sn for Q1:
main()
{
int a=5,b=10;
a=a+b;
b=a-b;
a=a-b;
printf("%d %d",a,b);
getch();
}

Question { RR Donnelley, 40832 }

What is the number of zeros of the product of the first 100
numbers ?

Answer

zeros result from either 5*2 or 10*1

5! = 12 0
10! = 36288 00
15! = 1307674368 000 and so on...

we have ten sets of 5*1 and 10*1 upto 100 and also two zeros
in 100...

so the answer is 21