$A$ man sells a scooter to his friend at $10\%$ loss. If the friend sells it for $₹ 54000$ and gains $20\%$,find out the original cost price of the scooter. (in $₹$)

The difference between successive discounts of $40\%$ followed by $30\%$ and $45\%$ followed by $20\%$ on the marked price of an article is $Rs. 12$. The marked price of the article is (in $Rs.$)

$A$ shopkeeper allows a discount of $10 \%$ on the marked price of a camera. The marked price of the camera,which costs him $₹ 600$,to make a profit of $20 \%$ should be (in $₹$):

Nutan pays $Rs. 2140$ for $3$ calculators and $4$ pens,while she pays $Rs. 1355$ for $1$ additional calculator and $5$ pens. What is the cost of a calculator in $Rs.$?

$A$ person earns $15 \%$ on an investment but loses $10 \%$ on another investment. If the ratio of the two investments is $3:5$,what is the gain or loss percentage on the two investments taken together (in $\%$)?

Mahesh purchased $25\, kg$ of rice at $Rs. 32$ per $kg$ and $15\, kg$ of rice at $Rs. 36$ per $kg.$ He mixed the two varieties of rice and sold it at $Rs. 40.20$ per $kg.$ What is the percent profit earned (in $\%$)?