A and B can complete a piece of work in 25 days and 55 days, respectively. The total number of days (in whole number) to complete the work, if A and B both work together, is:

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SSC Selection Post 2024 (Matriculation Level) Official Paper (Held On: 26 Jun, 2024 Shift 1)
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  1. 21
  2. 22
  3. 18
  4. 20

Answer (Detailed Solution Below)

Option 3 : 18
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Given:

A can complete the work in 25 days.

B can complete the work in 55 days.

Formula Used:

Work done by A and B together in one day = (1 / A's time) + (1 / B's time)

Total time to complete the work = 1 / (Work done by A and B together in one day)

Calculation:

Work done by A in one day = 1 / 25

Work done by B in one day = 1 / 55

Work done by A and B together in one day = (1 / 25) + (1 / 55)

⇒ Work done by A and B together in one day = (1)/(25) + (1)/(55)

⇒ Work done by A and B together in one day = (55 + 25)/(25 × 55)

⇒ Work done by A and B together in one day = (80)/(1375)

⇒ Work done by A and B together in one day = (16)/(275)

Total time to complete the work = 1 / ((16)/(275))

⇒ Total time to complete the work = (275)/(16)

⇒ Total time to complete the work = 17.1875 days

Rounding to the whole number, total time = 18 days

The total number of days to complete the work if A and B both work together is 18 days.

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