For a project, it takes 10 days for Party A, 15 days for Party B and 20 days for Party C to do it alone. During the three people working together, Party A took sick leave and the project was completed in 6 days. How many days did Party A ask for sick leave?

Method 1:

Thinking: Assuming that A didn't take sick leave, first find out the total amount of work that A, B and C completed in 6 days; Then subtract the unit "1" from the total workload of three people, and the extra workload is the workload that a sick leave should complete; Divide this workload by A's work efficiency, which is the number of days A takes vacation. ..

Let the whole project be "1", then the working efficiency of Party A is110.

The work efficiency of B is115, and that of C is 1/20.

Assuming that A didn't take sick leave, the total workload completed by three people in six days is:

(110 ten115 ten1/20) X6 =13/10,

Then the workload completed by Party A in sick leave is:1310-1= 3/10,

Therefore, the sick days of Party A are: 3/10 ÷110 = 3 (days).

Method 2:

Thinking: First, find out the workload completed by Party B and Party C in 6 days; The rest of the workload is done by A alone. A did it for a few days? Find out how many days A is on vacation.

Solution: Let the whole project be "1", then:

The daily workload of Party A is110, that of Party B is115 and that of Party C is 1/20.

The workload completed by Party C and Party B within 6 days is as follows:

( 1/ 15 X 1/20)X6 = 7/ 10，

The rest is110 = 3/10 completed by A-7.

3/10 ÷110 = 3 (days), that is, in six days, Party A only did three things, that is, called in sick for three days: 6-3=3 (days).

A: A asked for sick leave for three days.