All 303 families

GB-17-05-001 · Inverse square proportion

y is inversely proportional to x². When x = 12, y = 722. Find y when x = 19.

Direct and Inverse Proportion (Inverse Square) Booklet p. 23
Method
1) Replace ∝ with = k (y = k/x²)
2) Sub in given pair to find k = yx²
3) Write general formula and sub in new x
Worked Example (GB-17-05-001)
1)
y=kx2y=\frac{k}{x^2}
2)
722=k122⇒k=103968722=\frac{k}{12^2}\Rightarrow k=103968
3)
y=103968x2y=\frac{103968}{x^2}
4)
y=103968192=288y=\frac{103968}{19^2}=288
Ans = 288