Answer:
21
Step-by-step explanation:
factors of 42: 1,42, 2,<u>21</u>, 3,14, 6,7
factors of 63: 1,63, 3,<u>21</u>, 7,9
11/8 or 13/8 is the answer.
Alright, so we'd use the combinations with repetition formula, so we choose from 4 schools to distribute to and distribute 8 blackboards. It's then
( 8+4-1)!/8!(4-1)!=11!/(3!*8!)=165
For at least one blackboard, we first distribute 1 to each school and then have 4 blackboards left, getting (4+4-1)!/4!(4-1)!=7!/(4!*3!)=35
