Official Solution:Last year in the North Pole, 20% of all elves who crafted toys made wooden toys, while 40% of all elves who specialized in eco-friendly toy production made wooden toys. Last year in the North Pole, what percent of all elves who made wooden toys specialized in eco-friendly toy production? Set up a double-set matrix assuming the total number of elves to be \(x\), and the total number of elves who specialized in eco-friendly toy production is \(y\):
The question asks to find the value of \(\frac{0.4y}{0.2x}*100\), so essentially the ratio of \(y\) to \(x\).
(1) Last year in the North Pole, a total of 1,000 elves specialized in eco-friendly wooden toy production.
This implies that \(0.4y = 1,000\):
However, this does not help establish a relationship between \(x\) and \(y\). Not sufficient.
(2) Last year in the North Pole, 35% of all elves who crafted toys specialized in eco-friendly toy production.
This implies that \(y = 0.35x\):
With the ratio of \(y\) to \(x\) as \(35:100\), we can calculate the value of \(\frac{0.4y}{0.2x}*100\). Sufficient.
Answer: B