If $\frac{x}{y}+ \frac{y}{x}=\sqrt{7}$, What is the value of $\frac{x^4}{y^4}+\frac{y^4}{y^4}$ ?

The H.C.F. of two number is 11 and their LC.M. is 693. If one of the numbers is 77, find the other.

Silver is 17 times as heavy as water and copper is 7 times as heavy as water. In what ratio should these be mixed to get alloy 13 times as heavy as water?

The average of six numbers is 30. If the average of first four is 25 and that of last three is 35, the fourth number is :

A sum of TK. 600 amounts to TK. 720 in 4 years at simple interest. What will it amount to if the rate of interest is increased by 2% ?

In a mixture, the ratio of the milk and water is 65. When 22 liter D. 550 mixture is replaced by water, the ratio becomes 9: 13. What is the quantity of water after replacement?

Person 1 to 4 receive equal shares of an income, while Person 5 receives half of what each of Persons 1 to 4 receives. If the total Income is 18000 taka, how much does Person 5 get?