A can do a job in 10 days. B is 60 percent more efficient than A. In how many days can B alone complete the same job?

Introduction / Context:
Efficiency comparisons translate into rate multipliers. If B is 60 percent more efficient than A, B’s work rate is 1.6 times A’s rate. Time is the reciprocal of rate for one whole job.

Given Data / Assumptions:

• A time = 10 days ⇒ A rate = 1/10 per day.
• B efficiency = 160 percent of A.

Concept / Approach:
Multiply A’s rate by 1.6 to get B’s rate, then take the reciprocal to obtain B’s time to finish one job.

Step-by-Step Solution:

Verification / Alternative check:
If A does 1 unit in 10 days, in 6.25 days A would do 0.625 units. Since B is 1.6 times as fast, B’s output in 6.25 days is 1 unit, confirming the calculation.

Why Other Options Are Wrong:
6 and 6 2/3 arise from rounding or misinterpreting 60 percent more as 60 percent of A; 8 days assumes B is slower than reality; 5 days overestimates B’s efficiency.

Common Pitfalls:
Confusing 60 percent more with 60 percent of; converting 0.25 to fractional days incorrectly; mixing time and rate comparisons directly.

Final Answer:
6 1/4