2.5/6 molecules are magnified five times. To change the fractional value, the denominator should be enlarged by 5 times, and the numerator should be added with 15. To keep the decimal value unchanged, the denominator should be added (18).
3. Write three equal scores with the numbers 2, 3, 4, 6, 9, 18, and use each number only once. These three scores are (2/4, 3/6, 9/ 18).
4. Compare the scores of each group: 1.55 1/555 and 773/777 2.44445/4446 and 6667/6669.
55 1/555773/777;
44445/44446 & lt； 66667/66669.
5. A project needs to be completed in 65,438+0/3 days, 65,438+00 days and 65,438+0/9 days. So, who is the fastest among A, B and C?
It takes 4/( 1/3)= 12 days to complete the project;
B: 10 days to complete the project;
C project completion time: 1/( 1/9)=9 days.
Those who finish the project in the least number of days will finish it faster, so C finishes it fastest.
6。 Add 2 to the numerator of the fraction and subtract 2 from the denominator. The difference between the numerator and denominator of the new score is 123, and 8/49 is obtained after reduction. Find the original score.
Now the difference between the numerator and denominator of the fraction is:
49-8=4 1
Originally, the difference between the numerator and denominator of the new score was 123, but now it is only 4 1, 123/4 1 = 3 after divisor, so the numerator and denominator are divided by 3 at the same time.
Now restore: (8*3)/(49*3)=24/ 147.
Original score: (24-2)/(147+2) = 22/149.
7。 In the formula ()/()+()/() =112, it is required that both fractions are the simplest fractions with denominator less than 20. Please write the original formula according to the above information.
(2)/(3)+( 1)/(4)= 1 1/ 12
8. 1 minus 13 1/25 equals (12) 1/25, writing (12)/(25); 1115 plus (4) (1)/( 15) equals the smallest odd number.
9. Niu Niu drank a glass of milk four times. The first time he drank a cup of 1/5, and then filled it with water. The second time he drank 1/4, and then filled it with water. The third time he drank a cup of 1/2, and then filled it with water. The fourth time, he drank it all at once. Niu Niu drank too much milk.
As much.
I drank a glass of milk and water.
10. Three people have different deposits. If A gives B 40 yuan, B gives C 30 yuan, C gives A 20 yuan and B 70 yuan, then all three people have 240 yuan. What is their original deposit?
A: 240+40-20=260 yuan.
B: 240-40+30-70= 160 (RMB)
C: 240-30+20+70=300 yuan.
1 1. Simple calculation method:
20- 1/ 18+7/2 1-5/ 18
=20-( 1/ 18+5/ 18)+7/2 1
=20- 1/3+7/2 1
=20-7/2 1+7/2 1
=20
5/7-(3/5-2/7)
=5/7-3/5+2/7
= 1-3/5
=2/5
5/8-(3/8+ 1/ 12)
=5/8-3/8- 1/ 12
= 1/4- 1/ 12
=3/ 12- 1/ 12
= 1/6
12. 1/2 + 1/6 + 1/ 12 + 1/20 + 1/30 +......+ 1/2008*2009
= 1- 1/2+( 1/2- 1/3)+( 1/3- 1/4)+……+( 1/2008- 1/2009)
= 1- 1/2+ 1/2- 1/3+ 1/3- 1/4+……+ 1/2008- 1/2009
= 1- 1/2009
=2008/2009
13. Solve the equation:
X+7/ 13 = 39/78 * 4/3
Solution: X=2/3-7/ 13
X=5/39