In the  given figure , triangle s ABC and DEF are  similar. The  are a of triangle  ABC is 9 sq. cm and the  are a of triangle  DEF is 16 sq. cm. If BC = 2.1 cm find the  length of EF.

1) 4.9 cm 
2) 6.8 cm
3) 2.8 cm
4) 9.4 cm

If the length of a median of an equilateral triangle is x cm, then its area is 

1) x² 
2) Ö3x² / 2
3) x² / Ö3
4) x² / 2 

If every side of a triangle is doubled, then increase in the area of the triangle is 

1) 100Ö2 % 
2) 200  %
3) 300  %
4) 400  % 

The length of the sides of ∆ABC are consecutive integers. If ∆ABC has the same perimeter as an equilateral triangle with a side of length 9cm, what is the length of the shor test side of ∆ABC? 

1) 8 
2) 6
3) 4
4) 10 

The length of each side of an equilateral triangle of area 4Ö3 cm², is 

1) 8 cm
2) 4 cm
3) Ö3 / 4 cm
4) 3 cm