$A$ speaks truth in $80 \%$ of the cases and $B$ in $90 \%$ of the cases. Find the percentage when they contradict each other in describing the same facts. (in $\%$)

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?

Sunil decided to donate $5 \%$ of his salary. On the day of donation,he changed his mind and donated $₹ 1687.50$,which was $75 \%$ of what he had decided earlier. How much is Sunil's salary?

In an examination in which full marks were $800,$ $A$ gets $20 \%$ more than $B,$ $B$ gets $20 \%$ more than $C,$ and $C$ gets $15 \%$ less than $D.$ If $A$ got $576,$ what percentage of full marks did $D$ get (approximately) (in $\%$)?

The greatest value among $16 \frac{2}{3} \%$,$6 \frac{2}{3} \%$,and $0.3$ is:

Sameer spends $24 \%$ of his monthly income on food and $15 \%$ on the education of his children. Of the remaining salary,he spends $25 \%$ on entertainment and $20 \%$ on conveyance. He is now left with $₹ 10736$. What is the monthly salary of Sameer?