Four mathematical problems No.1 road repair team plans to build a road 150 meters a day and complete it in 12 days. If it is to be completed two days in advance, how many meters should be built every day? No.2 two trains leave from two places at the same time and run in opposite directions. After 4.5 hours, the two trains meet at a distance of 9 km from the destination. The express train runs 42 km per hour. How many kilometers are there between the two places? 2 times, how many students are there in each grade? No.4 a hospital plans to use white cloth with a length of 30 meters and a width of 1.8 meters to make triangular towel for rescue with two right angles of 0.6 meters. How many can be made?

NO.1
150 × 12 ÷ (12 - 2) = 180m
NO.2
(42 - 9 × 2 △ 4.5 + 42) × 4.5 = 360 km
NO.3
Grade 5 = 45 ÷ (1.2 - 1) = 225
Sixth grade = 225 + 45 = 270
NO.4
30 × 1.8 △ (0.6 × 0.6) × 2 = 300

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