A square ABCD, L is the midpoint of side AB, M is the midpoint of side BC, N is the midpoint of side CD and O is the midpoint of side AD, then find the ratio of area of shaded region PQRS to the area of square ABCD.
A square ABCD, L is the midpoint of side AB, M is the midpoint of side BC, N is the midpoint of side CD and O is the midpoint of side AD, then find the ratio of area of shaded region PQRS to the area of square ABCD. Correct Answer 1 ∶ 5
[ alt="Assign 9 D2" src="//storage.googleapis.com/tb-img/production/19/04/Assign%209_D2.PNG">L and N are the midpoints, so DL ∥ BN.
Similarly, OC ∥ AM,
In ΔAQB, L is the midpoint of AB and LP ∥ BQ.
So, P is a midpoint of side AQ.
⇒ AP= (1/2) × AQ
⇒ AP/AQ = 1/2
Also, ΔAPL and ΔAQB are similar
⇒ Ratio of area of ΔAPL and ΔAQB = 1 ∶ 4
⇒ Area of ΔAPL = 1
⇒ Area of PLQB = 3
By symmetry,
⇒ Area of ΔAPL = ΔQMB = ΔNRC = ΔDOS = 1
⇒ Area of PLQB = RCMQ = DSRN = OSPA = 3
Now, Join mid points O and M,
⇒ Area of ΔAMB = ΔAOM = ΔMOC = ΔDOC = 5
⇒ Area of ABCD = 5 + 5 + 5+ 5 = 20
⇒ Area of AMCO = 5 + 5 = 10
⇒ Area of PQRS = area of AMCO – area of APSO – area of CRQM = 10 – 3 – 3 = 4
∴ Area of shaded region ∶ Area of ABCD = 4 ∶ 20 = 1 ∶ 5