Party A and Party B jointly build a canal, which is planned to be completed in 21 days. After 16 days of actual construction, the remaining tasks will be completed in 12 days by Party A, and the other tasks will be completed by Party B and Party A What is the efficiency ratio?

Party A and Party B jointly build a canal, which is planned to be completed in 21 days. After 16 days of actual construction, the remaining tasks will be completed in 12 days by Party A, and the other tasks will be completed by Party B and Party A What is the efficiency ratio?

The sum of efficiency of Party A and Party B is 1 / 21
16 days after the joint construction of team a and team B
The remaining tasks are 1-16 × 1 / 21 = 5 / 21
therefore
A efficiency = 5 / 21 / 12 = 5 / 252
B efficiency = 1 / 21-5 / 262 = 7 / 252
Efficiency ratio of a and B = 5:7

The lengths of ropes a and B are equal. Cut off 12 meters of rope a and connect 14 meters of rope B. at this time, the length of rope a is 1 / 3 of that of rope B. find the length of the two ropes
List the formulas

Let the original length of the rope be x meters
The equation is as follows
x-12=(x+14)/3
The solution of the equation is x = 25
A: the original length of the two ropes was 25 meters
It should be the process

Party A and Party B work together to build a road. The ratio of the planned road length between Party A and Party B is 9:7. As a result, when the task is completed, team a has built 5 / 8 of the total length of the road, 30 meters more than the plan. How many meters does team a plan to build?

There is a ribbon, the first time to use 3 / 5 of the total length, the second time to use 12 decimeters, then the remaining ribbon length is exactly 1 / 4
How many decimeters is this ribbon

4+1 =5
12÷( 1 -3/5 - 1/5)
= 12÷1/5
=12×5
=60 decimeters