The speed of a train varies inversely with its length. A 200 meters long train runs at a speed of 60 km/hr. In how much time will a 500 meters long train cover 96 km?

While selling an article for Rs 18450, a person suffered a loss of 50%. At what price he should have sold the article (in Rs) to earn a profit of 50%?

The length of the portion of the straight line 3x + 4y = 12 intercepted between the axes is : 

If a²=b+c, b²=c+a  and c²=a+b then the  value of $$ {1\over{1+a}}+{1\over{1+b}}+{1\over{1+c}}$$ is

What is the value of $${0.74×1.23×0.13\over (0.37)^{3}+(0.41)^{3}-8(0.39)^{3}}$$ ?

Find the standard deviation of the following data (rounded off to two decimal places). 

5, 3, 4, 7 

For what value of m will the system of equations 18x-72y+13=0 and 7x-my-17=0 have no solution?

A can do a piece of work in 20 days and B in 30 days. They work together for 7 days and then both leave the work.  Then C alone finishes the remaining work in 10 days. In how many days will C finish the full work?