$60 = ? \% \text{ of } 400$

In an entrance examination,Ritu scored $56\%$ marks,Smita scored $92\%$ marks,and Rina scored $634$ marks. The maximum marks of the examination are $875$. What are the average marks scored by all the three girls together?

In an election between two candidates,$60 \%$ of the voters cast their vote,out of which $4 \%$ of the votes were declared invalid. $A$ candidate received $7344$ votes,which were $75 \%$ of the total valid votes. Find the total number of votes enrolled in the election.

Peter could save $10 \%$ of his income. But two years later,when his income increased by $20 \%$,he could save the same amount as before. By what percentage has his expenditure increased?

Shruti decided to donate $12 \%$ of her salary to an orphanage. On the day of donation,she changed her mind and donated $Rs. 3150$,which was $75 \%$ of what she had decided earlier. How much is Shruti's salary?

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?