A can do a work in 20 days and B in 30 days. If they work on it together for 2 days, then what is the fraction of the work that is left?

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SSC CPO 2024 Official Paper-I (Held On: 27 Jun, 2024 Shift 1)
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  1. \(\frac{5}{8}\)
  2. \(\frac{3}{5}\)
  3. \(\frac{5}{7}\)
  4. \(\frac{5}{6}\)

Answer (Detailed Solution Below)

Option 4 : \(\frac{5}{6}\)
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SSC CPO : English Comprehension Sectional Test 1
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Detailed Solution

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Given:

A can do a work in 20 days.

B can do a work in 30 days.

They work together for 2 days.

Concept Used:

When two or more individuals work together, their combined work rate is the sum of their individual work rates.

Formula Used:

Work rate of A = 1/20 work/day

Work rate of B = 1/30 work/day

Combined work rate = (1/20 + 1/30) work/day

Fraction of work done = Combined work rate × Number of days they work together

Fraction of work left = 1 - Fraction of work done

Calculation:

Combined work rate = 1/20 + 1/30

⇒ Combined work rate = 3/60 + 2/60

⇒ Combined work rate = 5/60 = 1/12 work/day

Fraction of work done in 2 days = (1/12) × 2

⇒ Fraction of work done = 1/6

Fraction of work left = 1 - 1/6

⇒ Fraction of work left = 6/6 - 1/6

⇒ Fraction of work left = 5/6

∴ The fraction of the work that is left is 5/6.

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