How many 2

How many three lettered words can be formed from letters A B C D E G H if repeats are:
a) not allowed
b) allowed

Result

n1 =  210
n2 =  343

Solution:

n1=n1=7⋅ 6⋅ 5=210n_{1}=n_{ 1 }=7 \cdot \ 6 \cdot \ 5=210
n2=n2=7⋅ 7⋅ 7=343n_{2}=n_{ 2 }=7 \cdot \ 7 \cdot \ 7=343

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