mathematics help .... i have to submit the answersin an hour?

Question

ok help me out plz ...
1.P and Q working together an do a job 4 days, Q and R can do the same job in 3 days, P and R in 2.4 days. How long will they take to finish job independently.

2. 5 tables and 8 chairs costRs.11500, 3 tables and 5 chairs cost Rs.7000. What is the cost of chair and table.

3.If 1 pump an fill a pool in 16 hrs and if 2 pumps can fill the pool in 6 hrs, how fast can 2 pump fill the pool

4. If 8 men take 12 days to assemble 16 machines how many days will it take 15 men to assemble 50 machines

Answer 1

PROBLEM 1:

P does 1/p of the job in a day
Q does 1/q of the job in a day
R does 1/r of the job in a day

Equation 1:
1/p + 1/q = 1/4

Equation 2:
1/q + 1/r = 1/3

Equation 3:
1/p + 1/r = 1/2.4

Solve for 1/q and plug into #2:
1/q = 1/4 - 1/p
(1/4 - 1/p) + 1/r = 1/3
-1/p + 1/r = 1/3 - 1/4
-1/p + 1/r = 4/12 - 3/12 = 1/12

Now combine #2 and #3 by adding:
2/r = 1/2.4 + 1/12
2/r = 5/12 + 1/12
2/r = 6/12
2/r = 1/2
r = 2 * 2
r = 4

From equation #2
1/q + 1/4 = 1/3
1/q + 3/12 = 4/12
1/q = 1/12
q = 12

From equation #3
1/p + 1/4 = 1/2.4

1/p + 3/12 = 5/12
1/p = 2/12
1/p = 1/6
p = 6

Answer:
p would take 6 days
q would take 12 days
r would take 4 days

PROBLEM 2:

5T + 8C = 11500
3T + 5C = 7000

Multiply equation #1 by 3:
15T + 24C = 34500

Multiply equation #2 by 5:
15T + 25C = 35000

Subtract #1 from #2:
C = 500

Substitute back in to solve for T:
5T + 8(500) = 11500
5T = 11500 - 4000
5T = 7500
T = 1500

Answer:
Tables cost 1500
Chairs cost 500

PROBLEM 3:
Huh? You already said 2 pumps fill it in 6 hrs. Please rephrase your question.

PROBLEM 4:

(8 men x 12 days) / 16 machines = 6 days per machine per man

(15 men x n days ) / 50 machines = 6 days per machine per man

15n = 300
n = 20

Answer:
20 days.