Available proportional knowledge solutions:
The total amount of food is fixed, and the number of people is inversely proportional to the number of days to eat.
So,
Suppose the remaining grain can be eaten for x days.
(360+ 120)x = 360×( 15-3)
x=9
The remaining food can be eaten for 9 days.
2. Master and apprentice processed 100 parts at the same time. The master makes one every 6 minutes and the apprentice makes one every 9 minutes. When they finished the task, how many parts were processed respectively?
Master's efficacy: 1/6
Apprentice efficacy: 1/9
The efficiency ratio is 1/6: 1/9 = 3: 2.
The efficiency ratio is equal to the total work ratio.
So:
100×3/(3+2)=60 pieces-60 pieces processed by the master.
100×2/(3+2)=40-40 processed by the apprentice.
The ratio of Class One to Class Two is 8: 7. If eight students in class one transfer to class two, the ratio of class one to class two becomes 4: 5. How many people are there in each of the two classes?
8+7= 15,4+5=9
8÷(8/ 15-4/9)
=8÷4/45
=90 people-total number of people
90×8/ 15=48 people-original shift.
90-48=42 people-the original class two.
Analysis:
The total remains the same.
So the total number of people is "1"
The original category accounts for 8/(8+7)=8/ 15 of the total.
Now one category accounts for 4/(4+5)=4/9 of the total.
Therefore, 8 people were transferred, accounting for 8/ 15-4/9=4/45.
Total population: 8÷4/45=90 people.
Class one was originally 90×8/ 15=48 people.
Class 2 was originally 90×7/ 15=42 people.