How many positive integers of three different digits, each less than 400 can be formed from the ...
How many positive integers of three different digits, each less than 400 can be formed from the digits 1, 2, 3, 4, 5 and 6?
Answer/Solution
60
Steps/Work
For the # to be < 400 the 100s digit shud be < 4 => one out of 3 choices 1/2/3
if the 100s digit is 1 then 10s digit can be selected in 5C1 and the units digit can be selected in 4C1 ways ==> 5C1*4C1=20
the same is the case with 2 and 3 too.
hence answer is 20+20+20 = 60
ANSWER:B
if the 100s digit is 1 then 10s digit can be selected in 5C1 and the units digit can be selected in 4C1 ways ==> 5C1*4C1=20
the same is the case with 2 and 3 too.
hence answer is 20+20+20 = 60
ANSWER:B