Step 1: Let the cost price of A be \( x \).
A sells the article at a 10% profit, so the selling price of A is:
\[
\text{Selling Price of A} = x + 10% \times x = 1.1x.
\]
Step 2: B's Buying and Selling Prices.
B buys the article at 10% lesser than A, so B's cost price is:
\[
\text{Cost Price of B} = x - 10% \times x = 0.9x.
\]
B sells it at ₹18 lesser than A, so B's selling price is:
\[
\text{Selling Price of B} = 1.1x - 18.
\]
B's gain percentage is 20%, so:
\[
\frac{\text{Selling Price of B} - \text{Cost Price of B}}{\text{Cost Price of B}} \times 100 = 20.
\]
Substitute the values:
\[
\frac{(1.1x - 18) - 0.9x}{0.9x} \times 100 = 20.
\]
Simplify the equation:
\[
\frac{0.2x - 18}{0.9x} \times 100 = 20 \implies 0.2x - 18 = 1.8x \implies 18 = 1.6x \implies x = \frac{18}{1.6} = 11.25.
\]
Thus, the cost price of A is ₹11.25.
Final Answer: \[ \boxed{810} \]
A weight of $500\,$N is held on a smooth plane inclined at $30^\circ$ to the horizontal by a force $P$ acting at $30^\circ$ to the inclined plane as shown. Then the value of force $P$ is:
A steel wire of $20$ mm diameter is bent into a circular shape of $10$ m radius. If modulus of elasticity of wire is $2\times10^{5}\ \text{N/mm}^2$, then the maximum bending stress induced in wire is: