At what rate of simple interest will a sum of money double in 8 years?

In a proportion, the 1^st , 2^nd and 4^th  terms are 51, 68 and 108, respectively. What is the 3^rd term?

The price that Akbar should marks on a pair of shoes which costs him 1,200 to gain 12% after allowing a discount of 16% (in rupees) is-

$$ if \ {1\over x}+x=4,$$ then find $${1\over x^2}+x^2$$

A spherical metallic shell with 6 cm external radius weighs 6688 g. What is the thickness of the shell if the density of metal is 10.5 g per cm3? (Take л = 22/7)

If $${8+2\sqrt{3} \over 3\sqrt{3}+5}=a\sqrt{3}-b$$, then the value of a+b is equal to:

In ΔABC, if G is the centroid and AD is a median with length 9 cm, then the length of AG is:

A hemispherical bowl of internal radius 18 cm is full of liquid. This liquid is to be filled in cylindrical bottles each of radius 3 cm and height 6 cm. How many bottles are required to empty the bowl