(1) The circumference of a semicircle with an area of (14. 13) square meters is 15.42 meters.

3. 14*r+2r= 15.42, while r=3, s = 0.5 * 3.14 * 3 =14.

(2) A rope is 50 meters long. Take 3/5, 5/2 1 meter, leaving (14.5) meters.

50*2/5-5.5= 14.5

(3) The sum of a number and its own sum, difference and quotient is 12.2, and this number is (5.6).

X+x+0+ 1= 12.2, so x=5.6.

(4) In order to support social welfare undertakings, a city printed a welfare lottery with the highest number of seven digits and set up the first prize. Suppose you take part in the lucky draw, the probability of winning the first prize is (11000000).

1/ 10^7

(5) It is known that A=2 times 2 times 3 times 5 and B=2 times 3 times n. If the greatest common factor of A and B is 30, then n=( 5) and the least common multiple of A and B is (90).

A=2*2*3*5 B=2*3*n 30=2*3*5 Least common multiple =2*3*5*3=90.

(6) It is stipulated that A times B=A times B+A+B, then when (A times 2) times 1=29, A=( 4).

(A※2)※ 1 = 29 = A * 2+A+2+A * 2+A+2+ 1，A=4。

(7) The average score of Chinese and English in Xiao Qiang is 93. After the math scores were announced, his average score increased by 2 points, and Xiao Qiang's math score was (99).

95*3-93*2=99

(8) 20km, increase 1 and decrease 1kloc-0/, which is (19.8) km.

20*( 1+0. 1)*0. 1=2.2,22-2.2= 19.8

Second, the column calculation

(1) A number and four fifths of this number are divided by two thirds to get nine fifths. What's this number?

5/9 ×2/3÷( 1+4/5)

(2) 50% of A is equal to 8/9 of 108, and B is 3/5 of A. What is B?

108×8/9÷50%×3/5

(3) How much is 48 times of 51219 more than 70% 19?

48/5× 19/ 12- 19×70%

Verbs (short for verb) solve problems.

(1) There are 4500 chickens on a farm. Raising ducks is 7/9 of raising chickens, and raising geese is 3/8 of the total number of chickens and ducks. How many poultry are raised on this farm?

Raising ducks: 4500×7/9 = 3500.

Goose breeding: (4500+3500)×3/8=3000.

Total * * *: 4500+3500+3000 =11000.

(2) What is the area of the largest circle that can be cut by a square paper with a side length of 5 decimeters?

The diameter of the largest circle is the side length,

S = 3.14× (5/2 )× (5/2) =19.625 square decimeter.

(3) A pool has two water inlet pipes and one water outlet pipe. You can fill the pool by opening tube A for 4 hours, tube B for 5 hours and tube C for 3 hours. Now that all three pipes are open, how many hours can you fill the pool?

1÷ (1/4+1/5-1/3) = 60/7 hours

(4) It takes 65,438+02 hours for a project to be completed by Party A alone and 65,438+05 hours for Party B alone. Now Party A will do it for 9 hours first, and how many hours will it take for Party B to do the rest alone?

A works for 9 hours: 9×112 = 3/4.

Remaining: 1-3/4= 1/4, and Party B:1/4 ÷115 = 3.75 hours.

(5) Xiaohong's family of four traveled to Hainan and chose one of the two three-star hotels with the same price, service facilities and conditions at night. Hotel A: Full price for adults, half price for children, and hotel B: 20% discount for all ages. Please help Xiaohong and her sister think about which hotel is cheaper for them to stay in.

Solution: the price is a yuan/person, and the hotel is A: 2×a+2×0.5a=3a.

Hotel b: 4× a× 0.8 = 3.2a.

So Hotel A is cheap.