Hand writing out the Pareto principle - 80/20 with chalk on a blackboard.
Hand writing #1 (number one) with chalk on a blackboard.
Student standing at the blackboard writing with chalk
Student standing at the blackboard writing with chalk
Student standing at the blackboard writing with chalk
Student standing at the blackboard writing with chalk
Student standing at the blackboard writing with chalk
Student standing at the blackboard writing with chalk
Smiling female teacher holding a chalk and writing on the blackboard
Female hand writing formulas on blackboard with chalk close up 20s 4k.
Animation of purple chalk writing the English word 'chemistry' on a blackboard. Animation of purple chalk writing the English word chemistry on a black chalkboard.
Close up shot of hand of unrecognizable woman writing programming code with chalk on blackboard