### Instruction: The Smith family has 4 sons and 3 daughters.  In how many ways can they be seated in a row of 7 chairs such that all 3 girls sit next to each other?### Response: I need to count the number of arrangements of 7 children in a row such that the 3 girls form a block.
I can think of the block of 3 girls as a single unit, and then arrange the 4 boys and the unit in any order.
There are 5 units to arrange, so there are 5! ways to do that.
But within the unit of girls, there are 3! ways to arrange the girls themselves.