How does the grouping of objects help the shopkeeper ?

How does the ploughing of fields help in preservation of moisture in the soil?

Priya bought a pen for Rs 25 . 65 .He gave Rs 50 to the shopkeeper. How much money did he get back from the shopkeeper?

Raju bought a book for Rs 35 . 65 .He gave Rs 50 to the shopkeeper. How much money did he get back from the shopkeeper?

How does sprinkling of salt help in clearing the snow covered roads in hilly areas? Explain the phenomenon involved in the process.

The far point of a myopic person is 80 cm. In front of the eye. What is the power of the lens required to enable him to see very distant objects clearly ? In what way does the corrective lens help the person above?Does the lens magnify very distant objects?Explain.