Find out what half of 39° (angle ABD) Then subtract that from 180° (angle ABE). When the plain flus faster angle (ABD) gets smaller and angle (ABE) gets bigger. Hope that helps.
Answer:
7 people, 7 walls, 48 minutes
Each person paints 1 wall in 48 minutes
20 persons, 20 walls
Each person can paint 1 wall in 48 minutes so it will take 48 minutes.
The answer would be 254,340,000
The formula of combination is
We have
and
Hence, there are 1001 ways of arranging 10 records from 14 records