The natural number m, for which the coefficient of x in the binomial expansion of

$${\left( {{x^m} + {1 \over {{x^2}}}} \right)^{22}}$$ is 1540, is .............

Let $${\left( {2{x^2} + 3x + 4} \right)^{10}} = \sum\limits_{r = 0}^{20} {{a_r}{x^r}} $$

Then $${{{a_7}} \over {{a_{13}}}}$$ is equal to ______.

For a positive integer n,
$${\left( {1 + {1 \over x}} \right)^n}$$ is expanded
in increasing powers of x. If three consecutive
coefficients in this expansion are in the ratio,
2 : 5 : 12, then n is equal to________.

If C_r $$ \equiv $$ ²⁵C_r and
C₀ + 5.C₁ + 9.C₂ + .... + (101).C₂₅ = 2²⁵.k, then k is equal to _____.