The total surface area of a hemisphere is 166.23 sq cm, find its radius?

A wire of length 60 m is used to enclose a field which is in the shape of a right - angled triangle. The area of the field is 150 m² then, the largest side of the field has a length of: 

If a-6b = 3 then the value of a³-216b³-54ab is : 

In a certain year, the average monthly income of a person was Rs.3,400. For the first eight months of the years, his average monthly income was Rs. 3,160 and for the last five months, it was Rs.4,120. His income in the eighth month of the year was: 

The mean of four different observations is 17.5. When a new observation whose value 20 is added, what will be the new mean?   

For what value of m will the system of equations 17x+my+102=0 and 23x+299y+138=0 have infinite number of solutions? 

A mixture of 40 liters of milk and water contains 30% water. How much milk should be added to this mixture so that the new mixture contains 80% milk?