+1237 I have $3$ different mathematics textbooks, $2$ different psychology textbooks, and $2$ different chemistry textbooks. In how many ways can I place the $7$ textbooks on a bookshelf, in a row, if all three mathematics textbooks must be together?
+875
I have $3$ different mathematics textbooks, $2$ different psychology textbooks, and $2$ different chemistry textbooks. In how many ways can I place the $7$ textbooks on a bookshelf, in a row, if all three mathematics textbooks must be together?
Temporarily consider the group of three math books as one unit.
Then, 1 group + 2 psych + 2 chem can arrange to 5P5 = 120 ways.
But wait. You could arrange the three math books 6 different ways.
So all the possible arrangements is 120 • 6 = 720 ways.
.
+875
I have $3$ different mathematics textbooks, $2$ different psychology textbooks, and $2$ different chemistry textbooks. In how many ways can I place the $7$ textbooks on a bookshelf, in a row, if all three mathematics textbooks must be together?
Temporarily consider the group of three math books as one unit.
Then, 1 group + 2 psych + 2 chem can arrange to 5P5 = 120 ways.
But wait. You could arrange the three math books 6 different ways.
So all the possible arrangements is 120 • 6 = 720 ways.
.
