Given 11 slips of paper: each has label of first 11 prime numbers.
label will be 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31
4 slips are drawn randomly one by one without replacement,
probability of all drawn 4 slips range being 12 = ???
Total ways of drawing 4 slips from 11 without replacement= 11C4= (11*10*9*8)/24=330
for range to be 12, the drawn slip must have pairs of (5,17), (7,19), (11,23),(17,29) and (19,31)- 5 pairs
For Range to be 12, we can choose 1 pair out of 5 and remaining two slips label should have value between the selected pair
if (5,17) pair is chosen, then 7, 11, 13 can be chosen for other 2 number label in 3c2 ways= 3 ways
if (7,19) chosen, then 11, 13, 17 can be chosen for other two labels in 3c2 ways= 3 ways
if(11,23) chosen, then 13, 17, 19 to be chosen for other two labels in 3c2 ways= 3 ways
if (17, 29) chosen, then 19, 23 to be chosen for other two label in 1 ways.
if (19,31) chosen, then 23, 29 to be chosen for other two labels in 1 ways
Total= 3+3+3+1+1= 11 ways
Required probability= 11/330= 1/30