1.[1+(1-0.25)] * 200 = 350. If the number of black rabbits is 25% less than that of white rabbits, 50 rabbits are missing.

2. The original plan is 72+6=78 tons. 6/78=0.0769 saves about 7.7%.

3. The length of the second team repair accounts for 1-0.30-0.25=0.45 or 45% of the total length. Then the total length is 900/0.45 = 2000m.

4.***400 pieces, 75% completed, and the remaining 25%. =400*0.25= 100 pieces.

5. The interest is 1000*0.025=25 yuan, and the principal and interest are 1025 yuan.

We have walked 35 miles, and the midpoint is 50%. There is still 15% from the midpoint, which is 27km. Then the whole journey is 27/0. 15= 180 km.

7. The first price reduction is (1-0. 1)*8200=7380 yuan, and the second price reduction is (1-0./) * 7380 = 6642 yuan.

Why don't you know these questions? Pupils' problems.