If the sides of a triangle are doubled, then its area

The sides of a triangle are 5 cm, 12 cm and 13 cm. then its area is

If a, b and c are the sides of a right-angled triangle, where a > b > c, then what is the value of the expression (a + b + c) (a + b - c) (a - b + c) (a - b - c)?

If the area of a square is equal to the area of an equilateral triangle, the ratio of the side of the square and the side of the equilateral triangle is

A triangle has side lengths x cm, x + 31 cm and x + 26 cm. If its area is 126 square cm, then what is the value of x ?

The base of a triangle is 15 dm and its height is 12 dm. The height of another triangle of double the area and the base of which is 20 dm, is given by