How is currency depreciation related to import tariffs? In the news today they were talking about how the US is "threatening to increase proposed tariffs on Chinese imports from 10 percent to 25 percent."
One of the reasons they gave for this was that Chinese currency has depreciation 8% which rendered the previous 10% tariffs ineffective. The news even described China as "fiddling" with their currency as if it was intentional to get around tariffs. 
I'm wondering how these two are related. How does a currency being worth less effect the percent based tariffs?
Assume that a chinese company is selling a product for 100 RMB or 16 USD.

With the 10% tariff the cost for an american importer rises to 17.6 USD. 

If the the RMB depreciates 8% and the price in RMB is unchanged the importer pays 8% less in USD or 16.192 USD. 

Depreciating the RMB by 8% offsets (almost all of) the effect of the 10% tariff.

This calculation does not account for the fact that chinese imports get more expensive. If the good is manufactured using imported oil the cost of that oil will not be offset by the depreciated RMB.