alleryA is twice as fast as B. Working together they finish a job in 8 days. A alone would take:
A10 days
B16 days
C24 days
D12 days
Answer & Solution
Correct answer: D. 12 days
1. If B does one unit a day, A does two units a day.
2. Together they do 3 units a day.
3. In 8 days they finish the job, so the whole job is 3 x 8 = 24 units.
4. A alone does 2 units a day, so A needs 24 / 2 = 12 days.
5. As a check, B alone would need 24 days, which is twice A's time, exactly as stated.
_Source: syllabus Maths, Ch 11 'Direct and Inverse Proportions', S11.3 Inverse Proportion_
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