A sum borrowed under compound interest doubles itself in 10 years. When will it become fourfold of itself at the same rate of interest?

Two numbers are respectively 30% and 40% less than a third number. What percent is the first number of the second?

If A : B: C= 2 : 3 : 4, then $$ {A\over B}:{B\over C}:{C\over A}$$ is equal to 

If x:y=3:2 then the ratio $$ {2\ x^{2}+3\ y^{2}}:{3\ x^{2}}-{2\ {y^{2}}}$$ is equal to

Find the greatest perfect square number of 5 digits.

A man earns a profit of 60% when he sells an article at 4/3 of the original selling price. Find the percent profit he makes at original price.

Arun purchased 30 kg. of rice at the rate of Rs. 17.50 per kg. and another Rs. 30 kg. at a certain rate. He mixed the two and sold the entire quantity at the rate Rs. 18.60 per kg. and made 20% overall profit. At what price per kg. did he pruchase the lot of another 30 kg. rice?

Three science classes A, B and C take a Science test. The average score of class A is 83. The average score of class B is 76. The average score of class C is 85. The average score of class A and B is 79 and average score of class B and C is 81. Then the average score of classes A, B and C is