Multiple choice

Elliot and Ellis started working at a computer company where they made computer parts. It took Elliot 70 days and Ellis 60 days to make a computer that was ready to sell. They began making the computer together, but Elliot left the work after some days due to illness, and it took Ellis 47 days to finish the remaining work alone. After how many days did Elliot leave?

  1. 5 days

  2. 7 days

  3. 8 days

  4. 9 days

  5. 11 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let x be the days they worked together. (x/70 + x/60) + 47/60 = 1. (x/70 + x/60) = 13/60. x * (6+7)/420 = 13/60. x * 13/420 = 13/60. x = 420/60 = 7.

AI explanation

Using the least common multiple method, let the total work be the LCM of 70 and 60, which is 420 units. Elliot does 420 / 70 = 6 units daily and Ellis does 420 / 60 = 7 units daily. When Elliot leaves, Ellis works alone for 47 days to finish the remaining 47 * 7 = 329 units. This means the pair worked together on the first 420 - 329 = 91 units, and at their combined rate of 13 units per day, Elliot left after 91 / 13 = 7 days.

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