# Need help with question C

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#### Dr.Peterson

##### Elite Member
So your answer is ... 1/8 of a layer? Or what? Stating what you did in words, including what your answer is, would help us talk about it.

It appears that you found the sum of one brick and the layer of mortar below it to be 21/8 inch, and then you divided that by the 21 inch height needed. Is that really the correct operation, do you think?

One way to check is to make units explicit. You have 21/8 inch per layer, divided by 21 inches per wall; dividing inch/layer by inch/wall yields walls/layer. You want layers/wall!

You're very close to the answer.

##### New member
That’s two layers so would I do 21/8 divided by 21?

#### Dr.Peterson

##### Elite Member
You want to divide the height of the wall by the height of one layer. The height of the wall is 21, and the height of one layer is 21/8. So isn't it clear that you want to divide 21 by 21/8?? What do you get? Does it make more sense than 1/8?

##### New member
21! Thanks a lot!

Staff member