The problem involves determining the number of shares of stock B in the trader's portfolio. Let the number of shares of stock B be x, and those of stock C be y. The given conditions are:
First, calculate the value of stock A in the portfolio:
Total value of stock A = 10 × 120 = ₹1200
The remainder of the portfolio value comes from stocks B and C. Therefore,
Value of stocks B and C = 3300 - 1200 = ₹2100
The value of stocks B and C can also be expressed in terms of x and y:
90x + 150y = 2100
Now, solve the system of equations:
90x + 150(20 - x) = 2100
90x + 3000 - 150x = 2100
-60x + 3000 = 2100
-60x = 2100 - 3000
-60x = -900
x = 15
Thus, the number of shares of stock B is 15. This value falls within the specified range [15, 15].
For any natural number $k$, let $a_k = 3^k$. The smallest natural number $m$ for which \[ (a_1)^1 \times (a_2)^2 \times \dots \times (a_{20})^{20} \;<\; a_{21} \times a_{22} \times \dots \times a_{20+m} \] is: