The yield formula runs backwards as happily as forwards. Know the promise and the yield? The delivery is $m_a = \dfrac{Y \cdot m_t}{100}$ — the promise, taxed down to its fraction. Know the delivery and the yield? The promise was $m_t = \dfrac{100 \cdot m_a}{Y}$ — undo the tax and the paper's full number returns. In both, the ÷100 or ×100 is doing one honest job: turning a percent into a fraction, or a fraction back into a percent.

And carry this sanity rail into every answer: the theoretical yield is a CEILING, so $m_t$ must always come out at least as big as $m_a$. If your recovered promise lands below what the flask delivered, a rearrangement upstream is lying to you — no appeal, go back a line.