If the height of a triangle is decreased by $40 \%$ and its base is increased by $40 \%$,what will be the effect on its area?

If $200 \%$ of a number is $90,$ then what is the $80 \%$ of that number?

$A, B$ and $C$ start a business by investing $Rs. 70000$ that earns them a profit of $Rs. 42000$ at the end of the year. $A$ invests his share in the profit in a scheme that gives $10\%$ interest compounded annually and $B$ invests his share in a scheme that gives $20\%$ interest compounded annually. $A$ gets $Rs. 2520$ as interest at the end of $2$ years and $B$ gets an interest of $Rs. 4200$ at the end of one year. Find $C$'s investment in the business.

Two jars contain equal quantities of $40 \%$ alcohol. Swati changed the concentration of the first jar to $50 \%$ by adding extra quantity of pure alcohol. Sonali changed the concentration of the second jar to $50 \%$ by replacing a certain quantity of the solution with pure alcohol. By what percentage is the quantity of alcohol added by Swati more than that replaced by Sonali?

Ravi is $12$ years younger than Surya. Ravi's age is $40 \%$ of the sum of his and Surya's age. What will be Surya's age $9$ years hence?

If inflation increases at a rate of $8 \%$ p.a.,what will a $₹ 20$ article cost at the end of two years?