Inequality

Question

Ursula will build a fence using wooden planks and posts. Each plank is at least 11.5 centimeters and at most 12.5 centimeters wide. The fence will have 12 posts that are exactly 15 centimeters wide. The completed fence will be 9 meters wide. Write an inequality that describes the range of possibilities for p, the total number of wooden planks that will be used?

Answer 1

I would suggest starting by converting all to one unit. I changed everything to meters. Resulting in planks of 0.115m, 0.125m and posts of 0.15m.

 

First multiply the 12 posts * 0.15m to determine how much space the posts take up  posts=1.8m

 

subtract the 1.8m from the 9m to show how much space needs to be filled by the plans.          space remaining =7.2m

 

so now you need to divide 7.2m by 0.125m and by 0.115m to determine how many planks are required assuming that all of the planks were at the higher or lower limit of size

 

7.2/0.125m=57.6 planks         7.2/.115=62.6 planks

 

I would guess that they want only whole planks so I would round to 58 and 63 planks leading to the following inequality:

 

58<=p<=63