Inverse variation is xy = k. If x doubles, y halves. Find the product from one pair, then keep that product. Direct variation is the other leftover, in direct variation.
Same product, not the same ratio
x = 4 and y = 6 give k = 24, so when x = 8, y = 3. Ratios as a set are in fractions and ratios.
The short list is in ACT Math formulas.
The bottom line
xy = k. Do not treat it as y = kx.
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