If `^(n)P_r = 840` and `^(n)C_r = 35` then find the value of r.

If "^(5)P_r = 2^(6)P_(r - 1) then find thevalue of r.

If ^(n)P_r = 1814400 and ^(n)C_r = 45 , find ^(n+4)C_(r+3)

Find x if ^(n)P_r = x ^(n)C_r

If ^(5)P_r = 2 ^(6)P_(r-1) then the value of r is

If "^15C_3r = "^15C_(r+3) ,then the value of r is

If "^(2n)C_3 : "^nC_2 = 44:3 , then for which of the following values of r, the value of "^nC_r will be 15