What do you mean there is a horizontal cd on ab? a+b+c+d=
2, a proportional formula, each term is a natural number, the ratio is 0.4, the product of two external terms is 80, the latter term of a ratio is greater than the previous term 12, and this ratio can be written as (8:20=4: 10).
a:b=0.4，a+ 12=b，a=8，b=20
ad=80，d= 10
a:b=c:d，=c: 10=0.4 c=4
3. The sixth grade of a primary school is divided into three groups to participate in tree planting activities. The ratio of the first group to the second group is 5:4, and the ratio of the second group to the third group is 3: 2. It is known that the number of people in the first group is less than the sum of the number of people in the second and third groups 15. How many people took part in planting trees in the sixth grade?
Number of people in the first group A: Number of people in the second group b=5:4= 15: 12.
Number of group B: Number of group C = 3: 2 = 12: 8.
Number of people in the first group A: number of people in the second group B: number of people in the third group c= 15: 12:8.
15c= 12b=8a
a= 15c/8
b= 15c/ 12
a+ 15 = b+c 15c/8+ 15 = 15c/ 12+c c = 40，a=75，b=50
a+b+c=75+50+40= 165
When Wang Ming returned to his home 800 meters away from home, his sister ran to him with a puppy. Wang Ming walks 40 meters per minute, his sister runs 50 meters per minute, and his dog runs 160 meters per minute. After meeting Wang Ming, he has been shuttling back and forth between Wang Ming and his sister at the same speed. How many meters did the puppy run when Wang Ming and his sister were 80 meters away?
When the distance between Wang Ming and his sister is 800 meters to 80 meters, it takes (800-80)/(40+50)=8 minutes.
The distance a dog runs in 8 minutes = 8× 160 = 1280 meters.
There is a pasture where the grass grows evenly every day. If 24 sheep are released, the grass will be eaten in 6 days. If you put 2 1 sheep and eat the grass in 8 days, how many sheep can you put at most so that the grass can never be eaten?
The amount of grass eaten by 24 sheep in 6 days: 24×6= 144 heads * day.
The amount of grass eaten in the first 8 days of 265438 +0: 2 1×8= 168 heads * day.
The amount of new grass growing every day: (168-144) ÷ (8-6) =12 heads * day.
The maximum number of sheep is 12 in order that the grass in the pasture will never be eaten up.
6、2×3×4+4×6×8+。 . . +200×300×400 part 1×2×3+2×4×6+. . . + 100×200×300
( 1×2×3+2×4×6+。 . . + 100×200×300)/(2×3×4+4×6×8+。 . . +200×300×400)
[( 1×2×3)×( 1+2…… 100)]/[(2×3×4)*( 1+2+…… 100)]=( 1×2×3)/(2×3×4)= 1/4
(Recursive equation calculation) (Application problems must have equations)