We have 9 pens, of which 5 are green ink, 3 are red ink, and 1 is black. If we put the pens in a line, how many arrangements are possible

504 arrangements are possible

Step-by-step explanation:

Arrangements of n elements:

The number of arrangements of n elements is given by:

Arrangements of n elements, divided into groups:

The number of arrangements of n elements, divided into groups of elements is given by:

In this case:

9 pens, into groups of 5, 3 and 1. So

504 arrangements are possible

answer:   14

step-by-step explanation:          

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answer: 8 years

step-by-step explanation:

the explanation is that in 8 years the child will be 20 and in 8 years the father will be 40 and 20 is half of 40.