There are seven pairs of black shoes and 5 pairs of white shoes .Tey all are put into a box and shoes are drawn at a time.To ensure that at leat one pair of black shoes are taken out,what is the number of shoes required to be drawn out.
Select the correct option
A) 12  B) 13  C) 7  D) 18  E) 19
White shoes: 5*2= 
<gadget id="calculator">5*2</gadget>
<output>10</output>
10   Black shoes:  7*2= 
<gadget id="calculator"> 7*2</gadget>
<output>14</output>
14   Total shoes:  14+10= 
<gadget id="calculator"> 14+10</gadget>
<output>24</output>
24   Now, for the worst case,   1st- All the white shoes are taken out, so 10 shoes are drawn.   2nd- All the one sided (assume only left side) black shoes are drawn. So, another 7 shoes are drawn.   So, in the box left shoes are= 24-17= 
<gadget id="calculator">24-17</gadget>
<output>7</output>
7   Those 7 shoes are right sided black shoes.   So on the 18th draw we'll get the 1st right footed black shoe, i.e. the 1st pair of black shoe.   So, the no. of shoes required to be drawn out is: 18   ANSWER:18
<result>D</result>
There are seven pairs of black shoes and 5 pairs of white shoes .Tey all are put into a box and shoes are drawn at a time.To ensure that at leat one pair of black shoes are taken out,what is the number of shoes required to be drawn out.