Question

A can do worl in 21 days and
b. Caan in do in 24 days b started working and after few ddays a joined him to complete ghe work afyer how many days did a join if thw work is completed in 16daays

Answer 1

Answer:

9 days

Step-by-step explanation:

Assumption: They are both doing same work.

Let W be the whole piece of work.

Let x be the days when B is working alone.

Then, B and A will be working together for (16-x) days.

A does a piece of work in 21 days.

B does a piece of work in 24 days.

So, we have

x times (W/24) + (16-x) times (W/21+W/24) = W

Cancelling W throughout, on both sides, we have,

x(1/24)+(16-x)(1/21+1/24)=1

Solving this further, (factoring out 1/3 and multiplying by 3 on both sides),

$\frac{x}{8}+(16-x)(\frac{1}{7}+\frac{1}{8})=3$

Simplifying,

x/8+15(16-x)/56=3

7x+240-15x=3*56

240-168=8x

72=8x

x=9