Hi Candidate,

I'm sorry to say that the Question you have asked for regarding the value of - sigma from r=0 to r=10 r.10Cr.3 power r.(-2)power 10-r cannot be solved directly as simply solving, but you have to rather break it up in small quantities and numbers and then sum it up.

In such tricky and long time Questions asked in the examination, it's best to rather use the conventional method of solving which is by putting up the values in succession and summingbl it from r=1 to r=10. It will help you to save time for other questions.

Hope that this answer helps you!!