The product of numbers a and b is 5.5. If the number A is expanded 5 times and the number B is expanded 2 times, then the product of the numbers A and B is (55).

When calculating a number divided by 3.75, Xiao Ming regards division as a multiplication symbol, and the result is 225. The correct answer to this question is (16).

Solve the problem.

1. A machinery factory has 38 tons of coal, which has been burned for 10 days, burning 1.2 tons of coal on average every day. If the remaining coal burns 1.3 tons per day, how many days can it burn?

Combustion days = (38-10×1.2) ÷1.3 = 20 (days)

2. Use a piece of red paper with a length of 108 cm and a width of 80 cm to make some pennants with right angles of 27 cm and 16 cm respectively. How many noodles can you cook at most?

The maximum number of pennants = (108× 80) ÷ [(27×16) ÷ 2] = 40 (surface).

3. A clothing factory used to make a uniform with 3.8m cloth. After changing the cutting method, each set saves 0.2 meters of cloth. Now you can make 190 sets of uniform cloth. How many sets can you make?

Original number of groups = (3.8-0.2) ×190 ÷ 3.8 =180 (group)

4. A trapezoid, if the upper bottom is extended by 8 decimeters, the area will increase by 16 square meters, and it will become a parallelogram. If the upper bottom of the original trapezoid is 4 decimeters long, how many square decimeters is the area of the original trapezoid?

Delta area increased = 16m2 = 0.8m (that is, 8m) × 40m ÷2.

The height of delta is also the height of trapezoid, so the height of trapezoid is 40 meters, so

The area of the original trapezoid =(0.4+ 1.2)×40÷2=32 (square meter) =3200 (square decimeter).