Discussion

Explanation:

Let ‘x’ be the percentage of gold in the new ingot. Therefore, using rule of allegation.

Therefore, $\frac{72-X}{X-54}=\frac{24}{12}$

That gives, X = 60%

Alternately,

It would be better to use the weighted average approach here.

i.e. weighted average (X) = $\frac{24\times 54\%+12\times 72\%}{24+12}$

⇒ X = $\frac{2\times 54+72}{3}$ = 2 × 18 + 24 = 60%.

Hence, 60.

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