Subject :IMO Class : Class 7
ABCD is a rectangle. E and F are midpoints of AB and CB respectively. If the area of the shaded ∆AEF is 7 cm2, then the area of rectangle ABCD, in square centimetres, is
A28
B49
C35
D56
Ans 1:
Class : Class 9
how is the answer worked out?
Ans 2:
Class :
FIRST MAKE THAT SIMILAR 4 TRAINGLES INSIDE A RECTANGLE
WHOSE TOTAL AREA IS 28 CM SQUARE
NOW WE ARE LEFT WITH FOUR EQUALITERAL TRAINGLES ARE OF WHOSE ONE IS
1/2*L/2*B/2=LB/8
FOR FOUR TRAINGLES TOTAL AREA =4*LB/8=LB/2
NOW
LB=LB/2+28
LB/2=28
LB=56 CM SQAURE