#### Thank you for registering.

One of our academic counsellors will contact you within 1 working day.

Click to Chat

1800-5470-145

+91 7353221155

CART 0

• 0
MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping

# How many quadrilaterals can be drawn by joining the vertices of a convex polygon of 20 sides so that the quadrilateral do not have any side common with the polygon??

Tushar Makkar
37 Points
10 years ago

it is 20c4(can also be written as c(20,4))-20*c(18,2)+17*19-18

total no. of quadrilateral=c(20,4)

total no. of quadrilateral with one side commmon=20*c(18,2)

reason=let's fix one side then no. of ways to form a quadrilteral then no. of points left =18 to choose 2 so c(18,2) = no. of ways ... fixing 20 sides so multiply by 20

inthe similar way we can find with 2 side common and 3 side common...

i've used alternate +- sign because in the case we take one side common there will be cases in which both side common will come....

this is same as aUb=a+b-(a intersection b)

pls. approve the ans. if u like the ans.