Flag Algebra> p c...
question mark

no. of ways of selecting p & q from {1,2,3,.....,9,10} so that |p-q|<4

ashish kumar , 12 Years ago
Grade 12th Pass
anser 1 Answers
Manas Satish Bedmutha

Last Activity: 12 Years ago

Consider p<q and

Case I: q-p=3

For p=1,2,3,...,6,7  no. of values of q satisfying resp. values are in order, 7,6,5,,...,2,1.

Thus for p<q there are 21 options.

Now as |p-q|=3, we have other 21 pairs. In all, 42 for |p-q|=3.

Case II : diff.=2

There are 28+28=56 pairs as done by method in case I.

Case II : diff.=1

There are 36+36=72 pairs as done by method in case I.

Thus in all, no. of ways = 72+56+42 = 172.

 

star
LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

tv

Full Live Access

material

Study Material

removal

Live Doubts Solving

assignment

Daily Class Assignments