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13 problems match “proportions”. Clear

Fire extinguishers for a building ●○○○○ 10 ptsOne fire extinguisher is recommended for every 6,000 square feet of a building. How many fire extinguishers are needed for a building of 135,000 square feet? Give the smallest whole number of extinguishers that provides at least one per 6,000 square feet.
Fish population by tag and recapture ●●○○○ 20 ptsA biologist wants to estimate the number of fish in a lake. On May 1 she catches a random sample of 60 fish, tags them, and releases them. On September 1 she catches a random sample of 70 fish and finds that 3 of them are tagged. To estimate the number of fish in the lake on May 1, she assumes that 25% of the May 1 fish are no longer in the lake on September 1 (because of death and emigration), that 40% of the fish in the lake on September 1 were not in the lake on May 1 (because of births and immigration), and that the tagged and untagged fish in the September 1 sample are representative of the whole population. What number does she calculate for the number of fish in the lake on May 1?
Students who like to dance ●●○○○ 20 ptsOf the students attending a school party, $60\%$ are girls, and $40\%$ of the students like to dance. After these students are joined by $20$ more boys, all of whom like to dance, the party is now $58\%$ girls. How many students at the party now like to dance?