Which country has approved convalescent plasma is the method to treat people who are critically ill with COVID-19?

A person rows a distance of $$ {3{3\over4}{ \ km}}$$ upstream in $$ {1{1\over 2}{\ hours}}$$ and a distance of 13 km downstream in 2 hours. How much time ( in hours) will the person take to row a distance of 90 km in still water?

Direction: A shopkeeper has some kg. rice of same price. He sold 150 kg. rice at 25 Rs. per kg. and earned a profit of 25%, another 180 kg. rice is sold at a profit of 20% and rest are sold at a loss of 10%. If the shopkeeper earns Rs. 1230 profit on all the rice that he has sold then answers the following question:

Find the quantity of those rice that are sold at a loss of 10%. 

A kite is flying in the sky. The length of string between a point on the ground and kite is 420 m. The angle of elevation of string with the ground is 30^o. Assuming that there is no slack in the string, then what is the height (in metres) of the kite?

Which one is not a Internet protocol?