Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa

If C_r= _{}^{25}\textrm{C}_r and C_0+5\cdot C_1+9\cdot C_2+\cdots \cdots +(101)\cdot C_{25}=2^{25}\cdot k, then k is equal to _________.

 

Option: 1

15


Option: 2

30


Option: 3

51


Option: 4

27


Answers (1)

best_answer

Properties of Binomial Theorem and Binomial Coefficient

\sum_{r=1}^{n} r \times ^{n} C_{r} = n.2^{n-1}

 

Now,

General term for given series is: (4r + 1).25Cr

Applying summation

\\=4 \sum_{r=1}^{25} r \times \;\; ^{25} C_{r}+2^{25}\\ =4\times25\cdot 2^{24}+2^{25}=50\cdot2^{25}+2^{25}=(50+1)2^{25}=51\cdot2^{25}

k = 51

 

Posted by

seema garhwal

View full answer

JEE Main high-scoring chapters and topics

Study 40% syllabus and score up to 100% marks in JEE

Similar Questions

Trending Articles/News

anam-khan

BTech aspirant from north-east or UT? Apply for CSAB NEUT counselling 2025 today
anam-khan

JoSAA round 2 cut-off 2025 out; BTech closing ranks for top engineering courses at IITs
anam-khan

Goa Engineering Admission 2025: 1,415 eligible for BE seats; merit list on June 27

Latest Question