Answer:
290 centimetres
Step-by-step explanation:
The ratio of the length of the pieces of wood is 6 : 10 : 12.
We have to find the total ratio first:
6 + 10 + 12 = 28
The longer piece of wood has ratio 10.
The length of the original wooden plank is 812 centimetres, therefore, the length of the longer piece of wood is:
10/28 * 812 = 290 centimetres
