BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

two less than the middle digit

Expert replies
by sanju09 » Thu Mar 24, 2011 3:00 am
If a three-digit number is selected at random from the integers 100 to 999, inclusive, what is the probability that the first digit and the last digit of the integer will both be exactly two less than the middle digit?
A. 1:900
B. 7:900
C. 9:1000
D. 1:100
E. 7:100


McGraw Hills
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Join the discussion
Source: — Problem Solving |

by manpsingh87 » Thu Mar 24, 2011 3:25 am
sanju09 wrote:If a three-digit number is selected at random from the integers 100 to 999, inclusive, what is the probability that the first digit and the last digit of the integer will both be exactly two less than the middle digit?
A. 1:900
B. 7:900
C. 9:1000
D. 1:100
E. 7:100


McGraw Hills
out of 900 number any one can be picked out in 900C1 ways.

also 1 and 3 digit must be same.
therefore, favorable cases are (1,3),(2,4),(3,5),(4,6),(5,7),(6,8),(7,9)
therefore required probability is 7C1/900C1 = 7/900 hence B
O Excellence... my search for you is on... you can be far.. but not beyond my reach!
Join the discussion