A alone can complete a work in 16 days and B alone in 12 days. Starting with A, they work on alternate days. The total work will be completed in ______.
Question
A alone can complete a work in 16 days and B alone in 12 days. Starting with A, they work on alternate days. The total work will be completed in ______.
Solution 1
Sure, let's solve this step by step.
Step 1: First, we need to find out how much work A and B can do in a day.
A can complete the work in 16 days, so A's work rate is 1/16 of the work per day. B can complete the work in 12 days, so B's work rate is 1/12 of the work per day.
Step 2: Now, let's find out how much work they can do together in two days (since they are working on alternate days).
In two days, A and B together can do (1/16 + 1/12) = 7/96 of the work.
Step 3: Now, we need to find out how many such two-day pairs it will take to complete the work.
To find this, we divide 1 (the total work) by the work done in two days. So, 1/(7/96) = 96/7 ≈ 13.71.
Since they can't work for a fraction of a day, we round this up to the nearest whole number, which is 14.
Step 4: However, this is the number of two-day pairs, so the total number of days it will take to complete the work is 14 * 2 = 28 days.
So, starting with A, they will complete the work in 28 days.
Solution 2
Sure, let's solve this step by step.
Step 1: First, we need to find out how much work A and B can do in a day.
A can complete the work in 16 days, so A's one day work is 1/16. B can complete the work in 12 days, so B's one day work is 1/12.
Step 2: Now, let's find out how much work they can do together in two days (since they are working on alternate days).
In two days, A and B can do (1/16 + 1/12) work. To add these two fractions, we need to find a common denominator. The least common multiple of 16 and 12 is 48. So, the work they can do in two days is (3/48 + 4/48) = 7/48.
Step 3: Now, we need to find out how many such two-day pairs it will take to complete the work.
Since they can do 7/48 of the work in two days, the number of two-day pairs it will take to complete the work is 1 / (7/48) = 48/7 = 6.857 pairs.
Step 4: But we can't have a fraction of a two-day pair. So, we need to round up to the nearest whole number, which is 7 pairs. This means it will take 14 days for them to complete the work together.
Step 5: But remember, we rounded up. This means that after 14 days, they have done a little more than the work required. So, on the 14th day, A starts working and completes the work before the day is over.
So, the total work will be completed in less than 14 days.
Solution 3
To solve this problem, we first need to find out how much work A and B can do in one day.
- A's one day work = 1/16
- B's one day work = 1/12
Next, we find out how much work they can do together in two days (since they are working on alternate days).
- A and B's two day work = A's one day work + B's one day work = 1/16 + 1/12 = 7/96
Now, we need to find out how many such two-day pairs it will take to complete the work.
- Number of two-day pairs = 1 / (A and B's two day work) = 1 / (7/96) = 96/7 = 13.71
Since we can't have a fraction of a day, we round this up to 14 two-day pairs.
But remember, this is the number of two-day pairs, so the total number of days is 2 * 14 = 28 days.
So, starting with A, they will complete the work in 28 days.
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